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1.  Cloning, Characterization, Controlled Overexpression, and Inactivation of the Major Tributyrin Esterase Gene of Lactococcus lactis 
The gene encoding the major intracellular tributyrin esterase of Lactococcus lactis was cloned using degenerate DNA probes based on 19 known N-terminal amino acid residues of the purified enzyme. The gene, named estA, was sequenced and found to encode a protein of 258 amino acid residues. The transcription start site was mapped 233 nucleotides upstream of the start codon, and a canonical promoter sequence was identified. The deduced amino acid sequence of the estA product contained the typical GXSXG motif found in most lipases and esterases. The protein was overproduced up to 170-fold in L. lactis by use of the nisin-controlled expression system recently developed for lactic acid bacteria. The estA gene was inactivated by chromosomal integration of a temperature-sensitive integration vector. This resulted in the complete loss of esterase activity, which could then be recovered after complementation of the constructed esterase-deficient strain with the wild-type estA gene. This confirms that EstA is the main enzyme responsible for esterase activity in L. lactis. Purified recombinant enzyme showed a preference for short-chain acyl esters, surprisingly also including phospholipids. Medium- and long-acyl-chain lipids were also hydrolyzed, albeit less efficiently. Intermediate characteristics between esterases and lipases make intracellular lactococcal EstA difficult to classify in either of these two groups of esterolytic enzymes. We suggest that, in vivo, EstA could be involved in (phospho)lipid metabolism or cellular detoxification or both, as its sequence showed significant similarity to S-formylglutathione hydrolase (FGH) of Paracoccus denitrificans and human EstD (or FGH), which are part of a universal formaldehyde detoxification pathway.
PMCID: PMC91993  PMID: 10742212
2.  Crystallization and preliminary X-ray diffraction analysis of the cytosolic domain of a cation diffusion facilitator family protein 
Selenomethionine-substituted crystals of the cytosolic domain of the cation diffusion facilitator family protein from T. maritima diffracted X-rays to 2.5 Å and belonged to space group R32, with unit-cell parameters a = b = 97.7, c = 83.4 Å.
The cation diffusion facilitator (CDF) family proteins are ubiquitously distributed in the three domains of life and transport metals such as zinc and various heavy metals. Prokaryotic CDF proteins consists of an N-terminal putative six-transmembrane domain followed by a C-terminal cytosolic domain. The cytosolic domain of the CDF-family protein from Thermotoga maritima has been overexpressed, purified and crystallized. The selenomethionine-substituted crystals diffracted X-rays to 2.5 Å resolution using synchrotron radiation, belonged to space group R32, with unit-cell parameters a = b = 97.7, c = 83.4 Å, and are expected to contain one molecule in each asymmetric unit.
PMCID: PMC2376318  PMID: 17768351
cation diffusion facilitators; transporter; zinc; membrane proteins; cytosolic domain
3.  A Novel Lipolytic Enzyme Located in the Outer Membrane of Pseudomonas aeruginosa 
Journal of Bacteriology  1999;181(22):6977-6986.
A lipase-negative deletion mutant of Pseudomonas aeruginosa PAO1 still showed extracellular lipolytic activity toward short-chain p-nitrophenylesters. By screening a genomic DNA library of P. aeruginosa PAO1, an esterase gene, estA, was identified, cloned, and sequenced, revealing an open reading frame of 1,941 bp. The product of estA is a 69.5-kDa protein, which is probably processed by removal of an N-terminal signal peptide to yield a 67-kDa mature protein. A molecular mass of 66 kDa was determined for 35S-labeled EstA by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. The amino acid sequence of EstA indicated that the esterase is a member of a novel GDSL family of lipolytic enzymes. The estA gene showed high similarity to an open reading frame of unknown function located in the trpE-trpG region of P. putida and to a gene encoding an outer membrane esterase of Salmonella typhimurium. Amino acid sequence alignments led us to predict that this esterase is an autotransporter protein which possesses a carboxy-terminal β-barrel domain, allowing the secretion of the amino-terminal passenger domain harboring the catalytic activity. Expression of estA in P. aeruginosa and Escherichia coli and subsequent cell fractionation revealed that the enzyme was associated with the cellular membranes. Trypsin treatment of whole cells released a significant amount of esterase, indicating that the enzyme was located in the outer membrane with the catalytic domain exposed to the surface. To our knowledge, this esterase is unique in that it exemplifies in P. aeruginosa (i) the first enzyme identified in the outer membrane and (ii) the first example of a type IV secretion mechanism.
PMCID: PMC94172  PMID: 10559163
4.  Crystallization and preliminary X-ray diffraction analysis of the magnesium transporter CorA 
Full-length and soluble domains of the integral membrane protein CorA have been expressed, purified and crystallized. X-ray diffraction data have been collected and analyzed.
The full-length integral membrane protein CorA from Thermotoga maritima (TmCorA1–351) has been expressed in Escherichia coli and purified without membrane isolation. TmCorA1–351 crystallized in the monoclinic space group C2, with unit-cell parameters a = 214.25, b = 86.30, c = 181.53 Å, β = 112.23°. Native crystals diffracted to 3.7 Å using synchrotron radiation, but selenomethionine-substituted crystals rarely diffracted to better than 5.0 Å. All full-length protein crystals were highly mosaic and produced anisotropic diffraction patterns. To aid in crystallographic phasing, soluble domain constructs were screened and the periplasmic domain of CorA from Archaeoglobus fulgidus (AfCorA1–263) was crystallized in the hexagonal space group P6122, with unit-cell parameters a = b = 101.17, c = 142.87 Å. Native and SeMet-substituted AfCorA1–263 crystals diffracted to ∼3.0 Å using synchrotron radiation.
PMCID: PMC2150960  PMID: 16511288
membrane proteins; transporter; magnesium
5.  Crystallization and preliminary X-ray crystallographic analysis of EstE1, a new and thermostable esterase cloned from a metagenomic library 
Recombinant EstE1 protein with a histidine tag at the C-terminus was overexpressed in Escherichia coli strain BL21(DE3) and then purified by affinity chromatography. The protein was then crystallized at 290 K by the hanging-drop vapour-diffusion method.
EstE1, a new thermostable esterase, was isolated by functional screening of a metagenomic DNA library from thermal environment samples. This enzyme showed activity towards short-chain acyl derivatives of length C4–C6 at a temperature of 303–363 K and displayed a high thermostability above 353 K. EstE1 has 64 and 57% amino-acid sequence similarity to est pc-encoded carboxylesterase from Pyrobaculum calidifontis and AFEST from Archaeoglobus fulgidus, respectively. The recombinant protein with a histidine tag at the C-terminus was overexpressed in Escherichia coli strain BL21(DE3) and then purified by affinity chromatography. The protein was crystallized at 290 K by the hanging-drop vapour-diffusion method. X-ray diffraction data were collected to 2.3 Å resolution from an EstE1 crystal; the crystal belongs to space group P41212, with unit-cell parameters a = b = 73.71, c = 234.23 Å. Assuming the presence of four molecules in the asymmetric unit, the Matthews coefficient V M is calculated to be 2.2 Å3 Da−1 and the solvent content is 44.1%.
PMCID: PMC2150951  PMID: 16511287
EstE1; carboxyesterases; thermostable enzymes
6.  Alicyclobacillus acidocaldarius Thermophilic Esterase EST2's Activity in Milk and Cheese Models 
The aim of this work was to investigate the behavior of thermophilic esterase EST2 from Alicyclobacillus acidocaldarius in milk and cheese models. The pure enzyme was used to compare the EST2 hydrolytic activity to the activity of endogenous esterase EstA from Lactococcus lactis. The results indicate that EST2 exhibits 30-fold-higher esterase activity than EstA. As EstA has thioesterase activity, EST2 was assayed for this activity under the optimal conditions determined for EstA (namely, 30°C and pH 7.5). Although it is a thermophilic enzyme, EST2 exhibited eightfold-higher thioesterase activity than EstA with S-methyl thiobutanoate. The abilities of EST2 and EstA to synthesize short-chain fatty acid esters were compared. Two methods were developed to do this. In the first method a spectrophotometric assay was used to monitor the synthesis of esters by the pure enzymes using p-nitrophenol as the alcohol substrate. The synthetic activities were also evaluated under conditions that mimicked those present in milk and/or cheese. The second method involved evaluation of the synthetic abilities of the enzymes when they were directly added to a model cheese matrix. Substantial ester synthesis by EST2 was observed under both conditions. Finally, esterase and thioesterase activities were evaluated in milk using the purified EST2 enzyme and in the model cheese matrix using a strain of L. lactis NZ9000 harboring the EST2 gene and thus overproducing EST2. Both the esterase and thioesterase activities measured in milk and in the cheese matrix were much greater than the activities of the controls.
PMCID: PMC1472309  PMID: 16672457
7.  The Autotransporter Esterase EstA of Pseudomonas aeruginosa Is Required for Rhamnolipid Production, Cell Motility, and Biofilm Formation▿  
Journal of Bacteriology  2007;189(18):6695-6703.
Pseudomonas aeruginosa PAO1 produces the biodetergent rhamnolipid and secretes it into the extracellular environment. The role of rhamnolipids in the life cycle and pathogenicity of P. aeruginosa has not been completely understood, but they are known to affect outer membrane composition, cell motility, and biofilm formation. This report is focused on the influence of the outer membrane-bound esterase EstA of P. aeruginosa PAO1 on rhamnolipid production. EstA is an autotransporter protein which exposes its catalytically active esterase domain on the cell surface. Here we report that the overexpression of EstA in the wild-type background of P. aeruginosa PAO1 results in an increased production of rhamnolipids whereas an estA deletion mutant produced only marginal amounts of rhamnolipids. Also the known rhamnolipid-dependent cellular motility and biofilm formation were affected. Although only a dependence of swarming motility on rhamnolipids has been known so far, the other kinds of motility displayed by P. aeruginosa PAO1, swimming and twitching, were also affected by an estA mutation. In order to demonstrate that EstA enzyme activity is responsible for these effects, inactive variant EstA* was constructed by replacement of the active serine by alanine. None of the mutant phenotypes could be complemented by expression of EstA*, demonstrating that the phenotypes affected by the estA mutation depend on the enzymatically active protein.
PMCID: PMC2045186  PMID: 17631636
8.  Preliminary X-ray analysis of twinned crystals of the Q88Y25_Lacpl esterase from Lactobacillus plantarum WCFS1 
The Q88Y25_Lacpl esterase from L. plantarum WCFS1 has been recombinantly expressed, purified and crystallized. A native diffraction data set has been collected to 2.24 Å resolution.
Q88Y25_Lacpl is an esterase produced by the lactic acid bacterium Lactobacillus plantarum WCFS1 that shows amino-acid sequence similarity to carboxyl­esterases from the hormone-sensitive lipase family, in particular the AFEST esterase from the archaeon Archaeoglobus fulgidus and the hyperthermophilic esterase EstEI isolated from a metagenomic library. N-­terminally His6-tagged Q88Y25_Lacpl has been overexpressed in Escherichia coli BL21 (DE3) cells, purified and crystallized at 291 K using the hanging-drop vapour-diffusion method. Mass spectrometry was used to determine the purity and homogeneity of the enzyme. Crystals of His6-tagged Q88Y25_Lacpl were prepared in a solution containing 2.8 M sodium acetate trihydrate pH 7.0. X-ray diffraction data were collected to 2.24 Å resolution on beamline ID29 at the ESRF. The apparent crystal point group was 422; however, initial global analysis of the intensity statistics (data processed with high symmetry in space group I422) and subsequent tests on data processed with low symmetry (space group I4) showed that the crystals were almost perfectly merohedrally twinned. Most probably, the true space group is I4, with unit-cell parameters a = 169.05, b = 169.05, c = 183.62 Å.
PMCID: PMC3212470  PMID: 22102251
Q88Y25_Lacpl; Lactobacillus plantarum; esterases; twinning
9.  Characterization of Esterase A, a Pseudomonas stutzeri A15 Autotransporter 
Autotransporters are a widespread family of proteins, generally known as virulence factors produced by Gram-negative bacteria. In this study, the esterase A (EstA) autotransporter of the rice root-colonizing beneficial bacterium Pseudomonas stutzeri A15 was characterized. A multiple sequence alignment identified EstA as belonging to clade II of the GDSL esterase family. Autologous overexpression allowed the investigation of several features of both autotransporter proteins and GDSL esterases. First, the correctly folded autotransporter was shown to be present in the membrane fraction. Unexpectedly, after separation of the membrane fraction, EstA was detected in the N-laurylsarcosine soluble fraction. However, evidence is presented for the surface exposure of EstA based on fluorescent labeling with EstA specific antibodies. Another remarkable feature is the occurrence of a C-terminal leucine residue instead of the canonical phenylalanine or tryptophan residue. Replacement of this residue with a phenylalanine residue reduced the stability of the β-barrel. Regarding the esterase passenger domain, we show the importance of the catalytic triad residues, with the serine and histidine residues being more critical than the aspartate residue. Furthermore, the growth of an estA-negative mutant was not impaired and cell mobility was not disabled compared to the wild type. No specific phenotype was detected for an estA-negative mutant. Overall, P. stutzeri A15 EstA is a new candidate for the surface display of proteins in environmentally relevant biotechnological applications.
PMCID: PMC3318783  PMID: 22307303
10.  Crystallization and preliminary X-ray crystallographic characterization of TrmFO, a folate-dependent tRNA methyltransferase from Thermotoga maritima  
T. maritima TrmFO was overexpressed, purified and crystallized. A diffraction data set was collected to a resolution of 2.6 Å.
TrmFO, previously classified as GID, is a methyltransferase that catalyzes the formation of 5-methyluridine or ribothymidine (T) at position 54 in tRNA in some Gram-positive bacteria. To date, TrmFO is the only characterized tRNA methyltransferase that does not use S-adenosylmethionine as the methyl-group donor. Instead, the donor of the methyl group is N 5,N 10-methylenetetra­hydrofolate. The crystallization and preliminary X-ray crystallographic studies of TrmFO are reported here. The recombinant protein, cloned from Thermotoga maritima genomic DNA, was overproduced in Esherichia coli and crystallized in 25%(v/v) PEG 4000, 100 mM NaCl and sodium citrate buffer pH 5.0 at 291 K using the hanging-drop vapor-diffusion method. The plate-shaped crystals diffracted to 2.6 Å and belong to the orthorhombic space group P212121, with unit-cell parameters a = 79.94, b = 92.46, c = 127.20 Å.
PMCID: PMC2374164  PMID: 18323606
GIDs; TrmFO; RNA modifications
11.  Gene cloning and characterization of a novel esterase from activated sludge metagenome 
A metagenomic library was prepared using pCC2FOS vector containing about 3.0 Gbp of community DNA from the microbial assemblage of activated sludge. Screening of a part of the un-amplified library resulted in the finding of 1 unique lipolytic clone capable of hydrolyzing tributyrin, in which an esterase gene was identified. This esterase/lipase gene consists of 834 bp and encodes a polypeptide (designated EstAS) of 277 amino acid residuals with a molecular mass of 31 kDa. Sequence analysis indicated that it showed 33% and 31% amino acid identity to esterase/lipase from Gemmata obscuriglobus UQM 2246 (ZP_02733109) and Yarrowia lipolytica CLIB122 (XP_504639), respectively; and several conserved regions were identified, including the putative active site, HSMGG, a catalytic triad (Ser92, His125 and Asp216) and a LHYFRG conserved motif. The EstAS was overexpressed, purified and shown to hydrolyse p-nitrophenyl (NP) esters of fatty acids with short chain lengths (≤ C8). This EstAS had optimal temperature and pH at 35°C and 9.0, respectively, by hydrolysis of p-NP hexanoate. It also exhibited the same level of stability over wide temperature and pH ranges and in the presence of metal ions or detergents. The high level of stability of esterase EstAS with its unique substrate specificities make itself highly useful for biotechnological applications.
PMCID: PMC3224729  PMID: 20028524
12.  Reverse Gyrase from the Hyperthermophilic Bacterium Thermotoga maritima: Properties and Gene Structure 
Journal of Bacteriology  1998;180(2):274-281.
The hyperthermophilic bacterium Thermotoga maritima MSB8 possesses a reverse gyrase whose enzymatic properties are very similar to those of archaeal reverse gyrases. It catalyzes the positive supercoiling of the DNA in an Mg2+- and ATP-dependent process. Its optimal temperature of activity is around 90°C, and it is highly thermostable. We have cloned and DNA sequenced the corresponding gene (T. maritima topR). This is the first report describing the analysis of a gene encoding a reverse gyrase in bacteria. The T. maritima topR gene codes for a protein of 1,104 amino acids with a deduced molecular weight of 128,259, a value in agreement with that estimated from the denaturing gel electrophoresis of the purified enzyme. Like its archaeal homologs, the T. maritima reverse gyrase exhibits helicase and topoisomerase domains, and its sequence matches very well the consensus sequence for six reverse gyrases now available. Phylogenetic analysis shows that all reverse gyrases, including the T. maritima enzyme, form a very homogeneous group, distinct from the type I 5′ topoisomerases of the TopA subfamily, for which we have previously isolated a representative gene in T. maritima (topA). The coexistence of these two distinct genes, coding for a reverse gyrase and an ω-like topoisomerase, respectively, together with the recent description of a gyrase in T. maritima (O. Guipaud, E. Marguet, K. M. Noll, C. Bouthier de la Tour, and P. Forterre, Proc. Natl. Acad. Sci. USA 94:10606–10611, 1977) addresses the question of the control of the supercoiling in this organism.
PMCID: PMC106882  PMID: 9440516
13.  Structure of EstA esterase from psychrotrophic Pseudoalteromonas sp. 643A covalently inhibited by monoethylphosphonate 
The crystal structure of the esterase EstA from a cold-adapted bacterium was determined in a form that was covalently inhibited by monoethylphosphonate.
The crystal structure of the esterase EstA from the cold-adapted bacterium Pseudoalteromonas sp. 643A was determined in a covalently inhibited form at a resolution of 1.35 Å. The enzyme has a typical SGNH hydrolase structure consisting of a single domain containing a five-stranded β-sheet, with three helices at the convex side and two helices at the concave side of the sheet, and is ornamented with a couple of very short helices at the domain edges. The active site is located in a groove and contains the classic catalytic triad of Ser, His and Asp. In the structure of the crystal soaked in diethyl p-nitrophenyl phosphate (DNP), the catalytic serine is covalently connected to a phosphonate moiety that clearly has only one ethyl group. This is the only example in the Protein Data Bank of a DNP-inhibited enzyme with covalently bound monoethylphosphate.
PMCID: PMC2795586  PMID: 19724118
esterases; psychrotrophic bacteria; monoethylphosphate inhibitors
14.  Crystal structure of hyperthermophilic esterase EstE1 and the relationship between its dimerization and thermostability properties 
EstE1 is a hyperthermophilic esterase belonging to the hormone-sensitive lipase family and was originally isolated by functional screening of a metagenomic library constructed from a thermal environmental sample. Dimers and oligomers may have been evolutionally selected in thermophiles because intersubunit interactions can confer thermostability on the proteins. The molecular mechanisms of thermostabilization of this extremely thermostable esterase are not well understood due to the lack of structural information.
Here we report for the first time the 2.1-Å resolution crystal structure of EstE1. The three-dimensional structure of EstE1 exhibits a classic α/β hydrolase fold with a central parallel-stranded beta sheet surrounded by alpha helices on both sides. The residues Ser154, Asp251, and His281 form the catalytic triad motif commonly found in other α/β hydrolases. EstE1 exists as a dimer that is formed by hydrophobic interactions and salt bridges. Circular dichroism spectroscopy and heat inactivation kinetic analysis of EstE1 mutants, which were generated by structure-based site-directed mutagenesis of amino acid residues participating in EstE1 dimerization, revealed that hydrophobic interactions through Val274 and Phe276 on the β8 strand of each monomer play a major role in the dimerization of EstE1. In contrast, the intermolecular salt bridges contribute less significantly to the dimerization and thermostability of EstE1.
Our results suggest that intermolecular hydrophobic interactions are essential for the hyperthermostability of EstE1. The molecular mechanism that allows EstE1 to endure high temperature will provide guideline for rational design of a thermostable esterase/lipase using the lipolytic enzymes showing structural similarity to EstE1.
PMCID: PMC1936996  PMID: 17625021
15.  Overproduction, purification, crystallization and preliminary X-ray analysis of the peroxiredoxin domain of a larger natural hybrid protein from Thermotoga maritima  
Crystals of the peroxiredoxin domain of a larger natural hybrid protein from T. maritima were obtained which diffracted to 2.9 Å resolution on a synchrotron source.
Thermotoga maritima contains a natural hybrid protein constituted of two moieties: a peroxiredoxin domain at the N-terminus and a nitroreductase domain at the C-terminus. The peroxiredoxin (Prx) domain has been overproduced and purified from Escherichia coli cells. The recombinant Prx domain, which is homologous to bacterial Prx BCP and plant Prx Q, folds properly into a stable protein that possesses biological activity. The recombinant protein was crystallized and synchrotron data were collected to 2.9 Å resolution. The crystals belonged to the tetragonal space group I422, with unit-cell parameters a = b = 176.67, c = 141.20 Å.
PMCID: PMC2374002  PMID: 18097097
natural hybrid proteins; Thermotoga maritima; peroxiredoxin domain
16.  Crystallization and preliminary X-ray crystallographic analysis of ligand-free and arginine-bound forms of Thermotoga maritima arginine-binding protein 
In this study, the hyperthermostable arginine-binding protein isolated from T. maritima has been crystallized in ligand-free and arginine-bound forms. Crystals of the apo and holo forms diffracted to 2.2 and 2.7 Å resolution, respectively.
The arginine-binding protein from Thermotoga maritima (TmArgBP) is an arginine-binding component of the ATP-binding cassette (ABC) transport system in this hyperthermophilic bacterium. This protein is endowed with an extraordinary stability towards thermal and chemical denaturation. Its structural characterization may provide useful insights for the clarification of structure–stability relationships and for the design of new biosensors. Crystallization trials were set up for both arginine-bound and ligand-free forms of TmArgBP and crystals suitable for crystallographic investigations were obtained for both forms. Ordered crystals of the arginine adduct of TmArgBP could only be obtained by using the detergent LDAO as an additive to the crystallization medium. These crystals were hexagonal, with unit-cell parameters a = 78.2, c = 434.7 Å, and diffracted to 2.7 Å resolution. The crystals of the ligand-free form were orthorhombic, with unit-cell parameters a = 51.8, b = 91.9, c = 117.9 Å, and diffracted to 2.25 Å resolution.
PMCID: PMC3212476  PMID: 22102257
hyperthermostable proteins; structure–stability relationships; amino-acid transport; biosensors
17.  Purification, crystallization and preliminary X-ray diffraction analysis of the putative ABC transporter ATP-binding protein from Thermotoga maritima  
The putative ABC transporter ATP-binding protein TM0222 from T. maritima was cloned, overproduced, purified and crystallized. A complete MAD diffraction data set has been collected to 2.3 Å resolution.
Adenosine triphosphate (ATP) binding cassette transporters (ABC transporters) are ATP hydrolysis-dependent transmembrane transporters. Here, the overproduction, purification and crystallization of the putative ABC transporter ATP-binding protein TM0222 from Thermotoga maritima are reported. The protein was crystallized in the hexagonal space group P6422, with unit-cell parameters a = b = 148.49, c = 106.96 Å, γ = 120.0°. Assuming the presence of two molecules in the asymmetric unit, the calculated V M is 2.84 Å3 Da−1, which corresponds to a solvent content of 56.6%. A three-wavelength MAD data set was collected to 2.3 Å resolution from SeMet-substituted TM0222 crystals. Data sets were collected on the BL38B1 beamline at SPring-8, Japan.
PMCID: PMC2496867  PMID: 18540059
ATP-binding proteins; transmembrane transporters; Thermotoga maritima; MAD data
18.  Biochemical and molecular characterization of the extracellular esterase from Streptomyces diastatochromogenes. 
Journal of Bacteriology  1996;178(7):1858-1865.
An esterase of Streptomyces diastatochromogenes was purified to homogeneity from culture filtrate. The purified enzyme had a molecular mass of 30,862 +/- 5.8 Da, as determined by electrospray mass spectrometry. The esterase-encoding gene was cloned on a 5.1-kb MboI fragment from S. diastatochromogenes genomic DNA into Streptomyces lividans TK23 by using plasmid vector pIJ702. Nucleotide sequence analysis predicted a 978-bp open reading frame, estA, encoding a protein of 326 amino acids, a potential ribosome binding site, and a putative 35- or 36-residue signal peptide for secretion in S. lividans or S. diastatochromogenes, respectively. The transcriptional initiation site was mapped 29 nucleotides upstream from the predicted translational start codon of estA in S. diastatochromogenes. The protein sequence deduced from the estA gene was similar to that of the esterase from the plant pathogen Streptomyces scabies. Both enzymes lacked the conserved motif GXSXG carrying the active-site serine of hydrolytic enzymes. A serine modified by [1,3-3H]diisopropyl fluorophosphate was located at position 11 of the mature enzyme in the sequence GDSYT. This finding and results obtained by site-directed mutagenesis studies indicate that serine 11 may be the active-site nucleophile.
PMCID: PMC177879  PMID: 8606158
19.  Use of Pseudomonas putida EstA as an Anchoring Motif for Display of a Periplasmic Enzyme on the Surface of Escherichia coli 
Applied and Environmental Microbiology  2004;70(12):6968-6976.
The functional expression of proteins on the surface of bacteria has proven important for numerous biotechnological applications. In this report, we investigated the N-terminal fusion display of the periplasmic enzyme β-lactamase (Bla) on the surface of Escherichia coli by using the translocator domain of the Pseudomonas putida outer membrane esterase (EstA), which is a member of the lipolytic autotransporter enzymes. To find out the transport function of a C-terminal domain of EstA, we generated a set of Bla-EstA fusion proteins containing N-terminally truncated derivatives of the EstA C-terminal domain. The surface exposure of the Bla moiety was verified by whole-cell immunoblots, protease accessibility, and fluorescence-activated cell sorting. The investigation of growth kinetics and host cell viability showed that the presence of the EstA translocator domain in the outer membrane neither inhibits cell growth nor affects cell viability. Furthermore, the surface-exposed Bla moiety was shown to be enzymatically active. These results demonstrate for the first time that the translocator domain of a lipolytic autotransporter enzyme is an effective anchoring motif for the functional display of heterologous passenger protein on the surface of E. coli. This investigation also provides a possible topological model of the EstA translocator domain, which might serve as a basis for the construction of fusion proteins containing heterologous passenger domains.
PMCID: PMC535197  PMID: 15574889
20.  Probing the applicability of autotransporter based surface display with the EstA autotransporter of Pseudomonas stutzeri A15 
Autotransporters represent a widespread family of secreted proteins in Gram-negative bacteria. Their seemingly easy secretion mechanism and modular structure make them interesting candidates for cell surface display of heterologous proteins. The most widely applied host organism for this purpose is Escherichia coli. Pseudomonas stutzeri A15 is an interesting candidate host for environmentally relevant biotechnological applications. With the recently characterized P. stutzeri A15 EstA autotransporter at hand, all tools for developing a surface display system for environmental use are available. More general, this system could serve as a case-study to test the broad applicability of autotransporter based surface display.
Based on the P. stutzeri A15 EstA autotransporter β-domain, a surface display expression module was constructed for use in P. stutzeri A15. Proof of concept of this module was presented by successful surface display of the original EstA passenger domain, which retained its full esterase activity. Almost all of the tested heterologous passenger domains however were not exposed at the cell surface of P. stutzeri A15, as assessed by whole cell proteinase K treatment. Only for a beta-lactamase protein, cell surface display in P. stutzeri A15 was comparable to presentation of the original EstA passenger domain. Development of expression modules based on the full-length EstA autotransporter did not resolve these problems.
Since only one of the tested heterologous passenger proteins could be displayed at the cell surface of P. stutzeri A15 to a notable extent, our results indicate that the EstA autotransporter cannot be regarded as a broad spectrum cell surface display system in P. stutzeri A15.
PMCID: PMC3546941  PMID: 23237539
Autodisplay; Proteinase K; Secretion; Type V secretion system; Outer membrane protein; Beta barrel
21.  Crystallization and preliminary crystallographic analysis of type 1 RNase H from the hyperthermophilic archaeon Sulfolobus tokodaii 7 
Type 1 RNase H from the hyperthermophilic archaeon S. tokodaii 7 was overproduced in E. coli, purified, and crystallized. Preliminary crystallographic studies indicated that the crystal belongs to space group P43, with unit-cell parameters a = b = 39.21, c = 91.15 Å.
Crystallization and preliminary crystallographic studies of type 1 RNase H from the hyperthermophilic archaeon Sulfolobus tokodaii 7 were performed. A crystal was grown at 277 K by the sitting-drop vapour-diffusion method. Native X-ray diffraction data were collected to 1.5 Å resolution using synchrotron radiation from station BL41XU at SPring-8. The crystal belongs to space group P43, with unit-cell parameters a = b = 39.21, c = 91.15 Å. Assuming the presence of one molecule in the asymmetric unit, the Matthews coefficient V M was calculated to be 2.1 Å3 Da−1 and the solvent content was 40.5%. The structure of a selenomethionine Sto-RNase HI mutant obtained using a MAD data set is currently being analysed.
PMCID: PMC2242919  PMID: 16880556
type 1 RNase H; Sulfolobus tokodaii 7
22.  Crystallization and preliminary crystallographic analysis of the cellulose biosynthesis-related protein CMCax from Acetobacter xylinum  
The cellulose biosynthesis-related protein CMCax from A. xylinum has been purified and crystallized. The crystals of CMCax belong to the primitive hexagonal space group P61 or P65, with unit-cell parameters a = b = 89.1, c = 94.2 Å.
The cellulose biosynthesis-related protein CMCax from Acetobacter xylinum was overexpressed in Escherichia coli, purified and crystallized. Single crystals of selenomethionine (SeMet) substituted CMCax were obtained by the hanging-drop vapour-diffusion method at 293 K, primarily using polyethylene glycol 4000 as a precipitant. The crystals belong to the primitive hexagonal space group P61 or P65, with unit-cell parameters a = b = 89.1, c = 94.2 Å. The predicted Matthews coefficient (V M) value is 3.0 Å3 Da−1 for one CMCax monomer in the asymmetric unit. A single-wavelength anomalous dispersion (SAD) data set was collected to a resolution of 2.3 Å using synchrotron radiation.
PMCID: PMC1952249  PMID: 16511009
Acetobacter xylinum; bacterial celluloses; cellulose biosynthesis; CMCax; endo-β-1,4-glucanases; glycoside hydrolase family 8
23.  Cloning, overexpression, purification, crystallization and preliminary X-ray diffraction analysis of an inositol monophosphatase family protein (SAS2203) from Staphylococcus aureus MSSA476 
The cloning, overexpression, purification, crystallization and preliminary X-ray diffraction analysis of an inositol monophosphatase family protein (SAS2203) from S. aureus MSSA476 is reported.
The gene product of the sas2203 ORF of Staphylococcus aureus MSSA476 encodes a 30 kDa molecular-weight protein with a high sequence resemblance (29% identity) to tetrameric inositol monophosphatase from Thermotoga maritima. The protein was cloned, expressed, purified to homogeneity and crystallized. Crystals appeared in several conditions and good diffraction-quality crystals were obtained from 0.2 M Li2SO4, 20% PEG 3350, 0.1 M HEPES pH 7.0 using the sitting-drop vapour-diffusion method. A complete diffraction data set was collected to 2.6 Å resolution using a Rigaku MicroMax-007 HF Cu Kα X-­ray generator and a Rigaku R-AXIS IV++ detector. The diffraction data were consistent with the orthorhombic space group P212121, with unit-cell parameters a = 49.98, b = 68.35, c = 143.79 Å, α = β = γ = 90°, and the crystal contained two molecules in the asymmetric unit.
PMCID: PMC3080153  PMID: 21505244
SAS2203; Staphylococcus aureus MSSA476; inositol monophosphatase family
24.  Cell Surface Expression of Bacterial Esterase A by Saccharomyces cerevisiae and Its Enhancement by Constitutive Activation of the Cellular Unfolded Protein Response▿ †  
Applied and Environmental Microbiology  2006;72(11):7140-7147.
Yeast cell surface display is a powerful tool for expression and immobilization of biocatalytically active proteins on a unicellular eukaryote. Here bacterial carboxylesterase EstA from Burkholderia gladioli was covalently anchored into the cell wall of Saccharomyces cerevisiae by in-frame fusion to the endogenous yeast proteins Kre1p, Cwp2p, and Flo1p. When p-nitrophenyl acetate was used as a substrate, the esterase specific activities of yeast expressing the protein fusions were 103 mU mg−1 protein for Kre1/EstA/Cwp2p and 72 mU mg−1 protein for Kre1/EstA/Flo1p. In vivo cell wall targeting was confirmed by esterase solubilization after laminarinase treatment and immunofluorescence microscopy. EstA expression resulted in cell wall-associated esterase activities of 2.72 U mg−1 protein for Kre1/EstA/Cwp2p and 1.27 U mg−1 protein for Kre1/EstA/Flo1p. Furthermore, esterase display on the yeast cell surface enabled the cells to effectively grow on the esterase-dependent carbon source glycerol triacetate (Triacetin). In the case of Kre1/EstA/Flo1p, in vivo maturation within the yeast secretory pathway and final incorporation into the wall were further enhanced when there was constitutive activation of the unfolded protein response pathway. Our results demonstrate that esterase cell surface display in yeast, which, as shown here, is remarkably more effective than EstA surface display in Escherichia coli, can be further optimized by activating the protein folding machinery in the eukaryotic secretion pathway.
PMCID: PMC1636145  PMID: 16980424
25.  Cloning, purification and preliminary crystallographic analysis of the Bacillus subtilis GTPase YphC–GDP complex 
Crystals of a selenomethionine-incorporated YphC–GDP complex have been grown using the hanging-drop vapour-diffusion method and polyethylene glycol as a precipitating agent.
The Bacillus subtilis YphC gene encodes an essential GTPase thought to be involved in ribosome binding and whose protein product may represent a target for the development of a novel antibacterial agent. Sequence analysis reveals that YphC belongs to the EngA family of GTPases, which uniquely contain two adjacent GTP-binding domains. Crystals of a selenomethionine-incorporated YphC–GDP complex have been grown using the hanging-drop vapour-diffusion method and polyethylene glycol as a precipitating agent. The crystals belong to space group P212121, with unit-cell parameters a = 62.71, b = 65.05, c = 110.61 Å, and have one molecule in the asymmetric unit. Data sets at three different wavelengths were collected on a single crystal to 2.5 Å resolution at the Daresbury SRS in order to solve the structure by MAD. Ultimately, analysis of YphC in complex with GDP may allow a greater understanding of the EngA family of essential GTPases.
PMCID: PMC2219971  PMID: 16682769
GTPase; EngA; YphC

Results 1-25 (295350)