Three conventional robots were subjected to a crystallization screening test involving 18 proteins from T. thermophilus HB8 using the sitting- and hanging-drop vapour-diffusion and microbatch methods. The number of diffraction-quality crystals and the amount of time required to obtain visible crystals depended greatly on the robots used. The combined use of different robots, especially for protein samples exhibiting low crystallization success rates, significantly increased the chance of obtaining diffraction-quality crystals.
It was essential for the structural genomics of Thermus thermophilus HB8 to efficiently crystallize a number of proteins. To this end, three conventional robots, an HTS-80 (sitting-drop vapour diffusion), a Crystal Finder (hanging-drop vapour diffusion) and a TERA (modified microbatch) robot, were subjected to a crystallization condition screening test involving 18 proteins from T. thermophilus HB8. In addition, a TOPAZ (microfluidic free-interface diffusion) designed specifically for initial screening was also briefly examined. The number of diffraction-quality crystals and the time of appearance of crystals increased in the order HTS-80, Crystal Finder, TERA. With the HTS-80 and Crystal Finder, the time of appearance was short and the rate of salt crystallization was low. With the TERA, the number of diffraction-quality crystals was high, while the time of appearance was long and the rate of salt crystallization was relatively high. For the protein samples exhibiting low crystallization success rates, there were few crystallization conditions that were common to the robots used. In some cases, the success rate depended greatly on the robot used. The TOPAZ showed the shortest time of appearance and the highest success rate, although the crystals obtained were too small for diffraction studies. These results showed that the combined use of different robots significantly increases the chance of obtaining crystals, especially for proteins exhibiting low crystallization success rates. The structures of 360 of 944 purified proteins have been successfully determined through the combined use of an HTS-80 and a TERA.
protein crystallization; crystallization screening; crystallization success rates
A cyclic olefin homopolymer-based microfluidics system has been established for protein crystallization and in situ X-ray diffraction.
Microfluidics is a promising technology for the rapid identification of protein crystallization conditions. However, most of the existing systems utilize silicone elastomers as the chip material which, despite its many benefits, is highly permeable to water vapour. This limits the time available for protein crystallization to less than a week. Here, the use of a cyclic olefin homopolymer-based microfluidics system for protein crystallization and in situ X-ray diffraction is described. Liquid handling in this system is performed in 2 mm thin transparent cards which contain 500 chambers, each with a volume of 320 nl. Microbatch, vapour-diffusion and free-interface diffusion protocols for protein crystallization were implemented and crystals were obtained of a number of proteins, including chicken lysozyme, bovine trypsin, a human p53 protein containing both the DNA-binding and oligomerization domains bound to DNA and a functionally important domain of Arabidopsis Morpheus’ molecule 1 (MOM1). The latter two polypeptides have not been crystallized previously. For X-ray diffraction analysis, either the cards were opened to allow mounting of the crystals on loops or the crystals were exposed to X-rays in situ. For lysozyme, an entire X-ray diffraction data set at 1.5 Å resolution was collected without removing the crystal from the card. Thus, cyclic olefin homopolymer-based microfluidics systems have the potential to further automate protein crystallization and structural genomics efforts.
cyclic olefin homopolymers; microfluidics; crystallization; in situ X-ray diffraction
The Microcapillary Protein Crystallization System (MPCS) is a new protein-crystallization technology used to generate nanolitre-sized crystallization experiments for crystal screening and optimization. Using the MPCS, diffraction-ready crystals were grown in the plastic MPCS CrystalCard and were used to solve the structure of methionine-R-sulfoxide reductase.
The Microcapillary Protein Crystallization System (MPCS) embodies a new semi-automated plug-based crystallization technology which enables nanolitre-volume screening of crystallization conditions in a plasticware format that allows crystals to be easily removed for traditional cryoprotection and X-ray diffraction data collection. Protein crystals grown in these plastic devices can be directly subjected to in situ X-ray diffraction studies. The MPCS integrates the formulation of crystallization cocktails with the preparation of the crystallization experiments. Within microfluidic Teflon tubing or the microfluidic circuitry of a plastic CrystalCard, ∼10–20 nl volume droplets are generated, each representing a microbatch-style crystallization experiment with a different chemical composition. The entire protein sample is utilized in crystallization experiments. Sparse-matrix screening and chemical gradient screening can be combined in one comprehensive ‘hybrid’ crystallization trial. The technology lends itself well to optimization by high-granularity gradient screening using optimization reagents such as precipitation agents, ligands or cryoprotectants.
protein crystallization; Microcapillary Protein Crystallization System
A thaumatin-like antifungal protein, NP24-I, has been isolated from ripe tomato fruits. It was crystallized by the vapour-diffusion method and data were collected to 2.45 Å. The structure was solved by molecular replacement.
NP24 is a 24 kDa (207-amino-acid) antifungal thaumatin-like protein (TLP) found in tomato fruits. An isoform of the protein, NP24-I, is reported to play a possible role in ripening of the fruit in addition to its antifungal properties. The protein has been isolated and purified and crystallized by the hanging-drop vapour-diffusion method. The crystals belong to the tetragonal space group P43, with unit-cell parameters a = b = 61.01, c = 62.90 Å and one molecule per asymmetric unit. X-ray diffraction data were processed to a resolution of 2.45 Å and the structure was solved by molecular replacement.
thaumatin-like protein; NP24 isoform; antifungal
A thermostable manganese(II)-dependent 2,3-dihydroxybiphenyl-1,2-dioxygenase derived from Bacillus sp. JF8 was crystallized in two forms using the sitting-drop vapour-diffusion method. Both crystals diffracted to approximately 1.3 Å resolution.
A thermostable manganese(II)-dependent 2,3-dihydroxybiphenyl-1,2-dioxygenase derived from Bacillus sp. JF8 was crystallized. The initial screening for crystallization was performed by the sitting-drop vapour-diffusion method using a crystallization robot, resulting in the growth of two crystal forms. The first crystal belonged to space group P1, with unit-cell parameters a = 62.7, b = 71.4, c = 93.6 Å, α = 71.2, β = 81.0, γ = 64.0°, and diffracted to 1.3 Å resolution. The second crystal belonged to space group I222, with unit-cell parameters a = 74.2, b = 90.8, c = 104.3 Å, and diffracted to 1.3 Å resolution. Molecular-replacement trials using homoprotocatechuate 2,3-dioxygenase from Arthrobacter globiformis (28% amino-acid sequence identity) as a search model provided a satisfactory solution for both crystal forms.
extradiol dioxygenases; crystallization robots; metalloproteins
The phasin PhaPAh from A. hydrophila strain 4AK4 was crystallized using the hanging-drop vapour-diffusion method.
Polyhydroxyalkanoate (PHA) granule-associated proteins (phasins) were discovered in PHA-accumulating bacteria. They play a crucial role as a structural protein during initial PHA-granule formation and granule growth and also serve as interfaces for granule stabilization in vivo. The phasin PhaPAh from Aeromonas hydrophila strain 4AK4 was crystallized using the hanging-drop vapour-diffusion method. Single crystals were cryocooled for X-ray diffraction analysis. The phasin crystals belonged to space group P212121, with unit-cell parameters a = 80.8, b = 108.9, c = 134.4 Å.
PHB; PHA; granule-associated proteins; phasins; polyhydroxyalkanoates; Aeromonas hydrophila
The digestive lysozymes 1 and 2 from M. domestica were crystallized by vapour diffusion. The crystallographic data were processed to a maximum resolution of 1.9 Å in both cases.
Lysozymes are mostly known for their defensive role against bacteria, but in several animals lysozymes have a digestive function. Here, the initial crystallographic characterization of two digestive lysozymes from Musca domestica are presented. The proteins were crystallized using the sitting-drop vapour-diffusion method in the presence of ammonium sulfate or PEG/2-propanol as the precipitant. X-ray diffraction data were collected to a maximum resolution of 1.9 Å using synchrotron radiation. The lysozyme 1 and 2 crystals belong to the monoclinic space group P21 (unit-cell parameters a = 36.52, b = 79.44, c = 45.20 Å, β = 102.97°) and the orthorhombic space group P21212 (unit-cell parameters a = 73.90, b = 96.40, c = 33.27 Å), respectively. The crystal structures were solved by molecular replacement and structure refinement is in progress.
digestive lysozymes; Musca domestica
The prototype of a universal micromanipulation robot for crystal harvesting is presented, and a robotically harvested trypsin crystal yields a high-resolution structure demonstrating the feasibility of robotic protein crystal harvesting.
High-throughput crystallography has reached a level of automation where complete computer-assisted robotic crystallization pipelines are capable of cocktail preparation, crystallization plate setup, and inspection and interpretation of results. While mounting of crystal pins, data collection and structure solution are highly automated, crystal harvesting and cryocooling remain formidable challenges towards full automation. To address the final frontier in achieving fully automated high-throughput crystallography, the prototype of an anthropomorphic six-axis universal micromanipulation robot (UMR) has been designed and tested; this UMR is capable of operator-assisted harvesting and cryoquenching of protein crystals as small as 10 µm from a variety of 96-well plates. The UMR is equipped with a versatile tool exchanger providing full operational flexibility. Trypsin crystals harvested and cryoquenched using the UMR have yielded a 1.5 Å structure demonstrating the feasibility of robotic protein crystal harvesting.
automated crystal harvesting; crystal mounting; cryoprotection; trypsin; protease; benzamidine complex; protamine; intermolecular contacts; crystallization additives
The Microcapillary Protein Crystallization System (MPCS) is used to successfully optimize protein crystals from 28 out of 29 tested proteins. Six protein structures have been determined from diffraction-ready crystals grown inside and harvested directly from the MPCS CrystalCards, which are compatible with the recently commercialized and automated MPCS Plug Maker instrument.
The Microcapillary Protein Crystallization System (MPCS) is a microfluidic, plug-based crystallization technology that generates X-ray diffraction-ready protein crystals in nanolitre volumes. In this study, 28 out of 29 (93%) proteins crystallized by traditional vapor diffusion experiments were successfully crystallized by chemical gradient optimization experiments using the MPCS technology. In total, 90 out of 120 (75%) protein/precipitant combinations leading to initial crystal hits from vapor diffusion experiments were successfully crystallized using MPCS technology. Many of the resulting crystals produced high-quality X-ray diffraction data, and six novel protein structures that were derived from crystals harvested from MPCS CrystalCards are reported.
protein crystals; microfluids; plugs; genomics
A high-resolution structure of human triosephosphate isomerase was obtained from crystals improved by means of the gel-tube method.
Crystals of human triosephosphate isomerase with two crystal morphologies were obtained using the normal vapour-diffusion technique with identical crystallization conditions. One had a disordered plate shape and the crystals were hollow (crystal form 1). As a result, this form was very fragile, diffracted to 2.8 Å resolution and had similar crystallographic parameters to those of the structure in the Protein Data Bank. The other had a fine needle shape (crystal form 2) and was formed more abundantly than crystal form 1, but was unsuitable for structure analysis. Since the normal vapour-diffusion method could not control the crystal morphology, gel-tube methods, both on earth and under microgravity, were applied for crystallization in order to control and improve the crystal quality. Whereas crystal form 1 was only slightly improved using this method, crystal form 2 was greatly improved and diffracted to 2.2 Å resolution. Crystal form 2 contained a homodimer in the asymmetric unit, which was biologically essential. Its overall structure was similar to that of except for the flexible loop, which was located at the active centre Lys13.
microgravity; triosephosphate isomerase; gel; counter-diffusion technique
BTL2, a thermostable enantioselective biocatalyst of interest for industrial applications, has been crystallized using the sitting-drop vapour-diffusion method. Preliminary X-ray data to 2.2 Å resolution allowed the determination of its unit-cell parameters and space group and initiation of its structure determination.
Bacillus thermocatenulatus lipase 2 (BTL2) is a thermoalkalophilic lipase that has been reported as an enantioselective biocatalyst for diverse reactions and that heads a group of enzymes that share high resistance towards many inactivation agents (heat, organic solvents, pH etc.). This makes BTL2 an important research target because of its potential industrial applications. BTL2 was cloned and overexpressed in Escherichia coli, purified and concentrated for crystallization using the sitting-drop vapour-diffusion method at 291 K. Crystals grew from a mixture of 13% MPD and 0.2 M ammonium acetate in 0.05 M sodium citrate pH 5.5–5.6. The crystals, which belonged to the orthorhombic space group I222 with unit-cell parameters a = 73.07, b = 129.08, c = 127.49 Å, allowed the collection of an X-ray data set to 2.2 Å resolution.
Bacillus thermocatenulatus; lipases
A preliminary X-ray crystal structural study of a soluble cognate T-cell receptor (TCR) in complex with a pMHC presenting the Melan-A peptide (ELAGIGILTV) is reported. The TCR and pMHC were refolded, purified and mixed together to form complexes, which were crystallized using the sitting-drop vapour-diffusion method. Single TCR–pMHC complex crystals were cryocooled and used for data collection.
Melanocytes are specialized pigmented cells that are found in all healthy skin tissue. In certain individuals, diseased melanocytes can form malignant tumours, melanomas, which cause the majority of skin-cancer-related deaths. The melanoma-associated antigenic peptides are presented on cell surfaces via the class I major histocompatibility complex (MHC). Among the melanoma-associated antigens, the melanoma self-antigen A/melanoma antigen recognized by T cells (Melan-A/MART-1) has attracted attention because of its wide expression in primary and metastatic melanomas. Here, a preliminary X-ray crystal structural study of a soluble cognate T-cell receptor (TCR) in complex with a pMHC presenting the Melan-A peptide (ELAGIGILTV) is reported. The TCR and pMHC were refolded, purified and mixed together to form complexes, which were crystallized using the sitting-drop vapour-diffusion method. Single TCR–pMHC complex crystals were cryocooled and used for data collection. Diffraction data showed that these crystals belonged to space group P41/P43, with unit-cell parameters a = b = 120.4, c = 81.6 Å. A complete data set was collected to 3.1 Å and the structure is currently being analysed.
Melan-A; T-cell receptors; class I MHC; HLA-A2
A method for growing crystals on cryoloops or micromounts is described, and diffraction patterns of crystals of three proteins grown by both the new method and the conventional drop method are compared. The study investigates the steps for the automation of the crystal growth and manipulation process and describes the design of a tray for the method.
Protein crystals are usually grown in hanging or sitting drops and generally get transferred to a loop or micromount for cryocooling and data collection. This paper describes a method for growing crystals on cryoloops for easier manipulation of the crystals for data collection. This study also investigates the steps for the automation of this process and describes the design of a new tray for the method. The diffraction patterns and the structures of three proteins grown by both the new method and the conventional hanging-drop method are compared. The new setup is optimized for the automation of the crystal mounting process. Researchers could prepare nanolitre drops under ordinary laboratory conditions by growing the crystals directly in loops or micromounts. As has been pointed out before, higher levels of supersaturation can be obtained in very small volumes, and the new method may help in the exploration of additional crystallization conditions.
protein crystallography; automation; crystal growth; cryoloops; micromounts
Biphenyl 2,3-dioxygenase from B. xenovorans LB400 and its variants BPDOP4 and BPDORR41 were crystallized using agarose gel and the crystals were characterized using X-ray diffraction.
Biphenyl 2,3-dioxygenase (BPDO; EC 18.104.22.168) catalyzes the initial step in the degradation of biphenyl and some polychlorinated biphenyls (PCBs). BPDOLB400, the terminal dioxygenase component from Burkholderia xenovorans LB400, a proteobacterial species that degrades a broad range of PCBs, has been crystallized under anaerobic conditions by sitting-drop vapour diffusion. Initial crystals obtained using various polyethylene glycols as precipitating agents diffracted to very low resolution (∼8 Å) and the recorded reflections were diffuse and poorly shaped. The quality of the crystals was significantly improved by the addition of 0.2% agarose to the crystallization cocktail. In the presence of agarose, wild-type BPDOLB400 crystals that diffracted to 2.4 Å resolution grew in space group P1. Crystals of the BPDOP4 and BPDORR41 variants of BPDOLB400 grew in space group P21.
biphenyl 2,3-dioxygenase; Burkholderia xenovorans LB400; agarose gel
SSGCID protein crystals were salvaged and stored using the MPCS Plug Maker and CrystalCards when high-throughput traditional sitting-drop vapor diffusion initially failed.
The MPCS Plug Maker is a microcapillary-based protein-crystallization system for generating diffraction-ready crystals from nanovolumes of protein. Crystallization screening using the Plug Maker was used as a salvage pathway for proteins that failed to crystallize during the initial observation period using the traditional sitting-drop vapor-diffusion method. Furthermore, the CrystalCards used to store the crystallization experiments set up by the Plug Maker are shown be a viable container for long-term storage of protein crystals without a discernable loss of diffraction quality with time. Use of the Plug Maker with SSGCID proteins is demonstrated to be an effective crystal-salvage and storage method.
microfluidics; salvage; storage
Wild-type and variant crystals of a recombinant enzyme β-d-glucan glucohydrolase from barley (Hordeum vulgare L.) were obtained by macroseeding and cross-seeding with microcrystals obtained from native plant protein. Crystals grew to dimensions of up to 500 × 250 × 375 μm at 277 K in the hanging-drops by vapour-diffusion. Further, the conditions are described that yielded the wild-type crystals with dimensions of 80 × 40 × 60 μm by self-nucleation vapour-diffusion in sitting-drops at 281 K. The wild-type and recombinant crystals prepared by seeding techniques achived full size within 5–14 days, while the wild-type crystals grown by self-nucleation appeared after 30 days and reached their maximum size after another two months. Both the wild-type and recombinant variant crystals, the latter altered in the key catalytic and substrate-binding residues Glu220, Trp434 and Arg158/Glu161 belonged to the P43212 tetragonal space group, i.e., the space group of the native microcrystals was retained in the newly grown recombinant crystals. The crystals diffracted beyond 1.57–1.95 Å and the cell dimensions were between a = b = 99.2–100.8 Å and c = 183.2–183.6 Å. With one molecule in the asymmetric unit, the calculated Matthews coefficients were between 3.4–3.5 Å3·Da−1 and the solvent contents varied between 63.4% and 64.5%. The macroseeding and cross-seeding techniques are advantageous, where a limited amount of variant proteins precludes screening of crystallisation conditions, or where variant proteins could not be crystallized.
macro- and cross-seeding; wild-type and mutant protein; X-ray diffraction
A novel l-amino-acid oxidase was isolated from V. ammodytes ammodytes venom and crystallized. The solution conditions under which the protein sample was monodisperse were optimized using dynamic light scattering prior to crystallization. Preliminary diffraction data were collected to 2.6 Å resolution.
l-Amino-acid oxidase from the venom of Vipera ammodytes ammodytes, the most venomous snake in Europe, was isolated and crystallized using the sitting-drop vapour-diffusion method. The solution conditions under which the protein sample was monodisperse were optimized using dynamic light scattering prior to crystallization. The crystals belonged to space group C2, with unit-cell parameters a = 198.37, b = 96.38, c = 109.11 Å, β = 92.56°. Initial diffraction data were collected to 2.6 Å resolution. The calculated Matthews coefficient is approximately 2.6 Å3 Da−1 assuming the presence of four molecules in the asymmetric unit.
l-amino-acid oxidase; snake venoms
Crystallization of the cystine-knot protein Spätzle occurred following serendipitous limited degradation of the pro-Spätzle propeptide during the crystallization experiment.
The Spätzle protein is involved in both the definition of the dorsal–ventral axis during embryonic development and in the adult innate immune response. The disulfide-linked dimeric cystine-knot protein has been expressed as a proprotein in inclusion bodies in Escherichia coli and refolded in vitro by rapid dilution. Initial orthorhombic crystals that diffracted to 7 Å resolution were obtained after three months by the sitting-drop vapour-diffusion method. Optimization of the crystallization conditions resulted in orthorhombic crystals (space group P212121, with unit-cell parameters a = 53.0, b = 59.2, c = 62.5 Å) that diffracted to 2.8 Å resolution in-house. The small volume of the asymmetric unit indicated that it was not possible for the crystals to contain the complete pro-Spätzle dimer. Mass spectrometry, N-terminal sequencing and Western-blot analysis revealed that the crystals contained the C-terminal disulfide-linked cystine-knot dimer. Comparison of various crystallization experiments indicated that degradation of the N-terminal prodomain was dependent on the buffer conditions.
degradation; growth factors; Toll pathway
A thermostable multicopper oxidase from Thermus thermophilus HB27 (Tth-MCO) has been successfully crystallized using the sitting-drop and hanging-drop vapour-diffusion methods.
A thermostable multicopper oxidase from Thermus thermophilus HB27 (Tth-MCO) was successfully crystallized using the sitting-drop and hanging-drop vapour-diffusion methods. Crystallization conditions and preliminary X-ray diffraction data to 1.5 Å resolution obtained using synchrotron radiation at 100 K are reported. The crystals belonged to space group C2221, with unit-cell parameters a = 93.6, b = 110.3, c = 96.3 Å. A monomer in the asymmetric unit yielded a Matthews coefficient (V
M) of 2.60 Å3 Da−1 and a solvent content of 53%. An inactive enzyme form, apo-Tth-MCO, was also crystallized and diffraction data were collected to 1.7 Å resolution. In addition, a second inactive form of the enzyme, Hg-Tth-MCO, was obtained by soaking apo-Tth-MCO crystals with mercury(II) chloride and data were collected to a resolution of 1.7 Å.
laccases; multicopper oxidases; Thermus thermophilus
Human prouroguanylin, a precursor protein of a peptide hormone, was expressed in E. coli, refolded, purified and crystallized. The crystals belong to space group P6122 and diffract X-rays to 2.5 Å resolution.
Uroguanylin, which serves as an endogenous ligand of guanylyl cyclase C, is initially secreted in the form of a precursor, prouroguanylin. The N-terminal region of prouroguanylin interacts with the mature portion of prouroguanylin during the folding pathway. Here, a preliminary X-ray crystallographic study of prouroguanylin is presented. Prouroguanylin was refolded, purified and crystallized using the hanging-drop vapour-diffusion method. Prouroguanylin crystals were cryocooled and used for data collection. The diffraction data showed that the crystals belonged to space group P6122, with unit-cell parameters a = b = 55.6, c = 157.7 Å, and diffracted to 2.5 Å resolution. The structure is currently being analyzed.
prouroguanylin; precursor proteins; peptide hormones
A core fragment of Arabidopsis thaliana COP9 signalosome (CSN) subunit 7 was expressed in Escherichia coli. The protein was purified to homogeneity and crystallized.
A core fragment of Arabidopsis thaliana COP9 signalosome (CSN) subunit 7 was expressed in Escherichia coli. The protein was purified to homogeneity and screened for crystallization. Crystallization conditions were refined using the sitting-drop vapour-diffusion method. Crystals were obtained using polyethylene glycol 8000 as a precipitant and have a thick rod-like morphology. Their crystallographic symmetry is orthorhombic, space group C2221, with unit-cell parameters a = 57.2, b = 86.2, c = 72.6 Å and a diffraction limit of 2.06 Å.
COP9 signalosome; proteasome; PCI and MPN motifs
The electron-transfer complex of BphA3, a Rieske-type [2Fe–2S] ferredoxin, and BphA4, a NADH-dependent ferredoxin reductase, was crystallized by the sitting-drop vapour-diffusion method under anaerobic conditions.
The electron-transfer complex of BphA3, a Rieske-type [2Fe–2S] ferredoxin, and BphA4, a NADH-dependent ferredoxin reductase, was crystallized using the sitting-drop vapour-diffusion method under anaerobic conditions. The obtained crystals were analyzed by SDS–PAGE, which showed that they contained both BphA3 and BphA4. The crystals belong to space group P21, with unit-cell parameters a = 60.60, b = 173.72, c = 60.98 Å, β = 115.8°, and diffracted to a resolution of 1.9 Å.
electron-transfer complexes; ferredoxins; NADH-dependent ferredoxin reductases; anaerobic conditions
The bifunctional enzyme catalase-phenol oxidase from S. thermophilum was crystallized by the hanging-drop vapour-diffusion method in space group P21 and diffraction data were collected to 2.8 Å resolution.
Catalase-phenol oxidase from Scytalidium thermophilum is a bifunctional enzyme: its major activity is the catalase-mediated decomposition of hydrogen peroxide, but it also catalyzes phenol oxidation. To understand the structural basis of this dual functionality, the enzyme, which has been shown to be a tetramer in solution, has been purified by anion-exchange and gel-filtration chromatography and has been crystallized using the hanging-drop vapour-diffusion technique. Streak-seeding was used to obtain larger crystals suitable for X-ray analysis. Diffraction data were collected to 2.8 Å resolution at the Daresbury Synchrotron Radiation Source. The crystals belonged to space group P21 and contained one tetramer per asymmetric unit.
Scytalidium thermophilum; Humicola insolens; catalases; phenol oxidases; catechol oxidases; CATPO
Single crystals of 6-aminohexanoate-dimer hydrolase have been prepared by the sitting-drop vapour-diffusion method using ammonium sulfate as a precipitant. Diffraction data were collected from native and methylmercuric chloride derivative crystals to resolutions of 1.75 and 1.80 Å, respectively.
To investigate the structure–function relationship between 6-aminohexanoate-dimer hydrolase (EII) from Arthrobacter sp. and a cryptic protein (EII′) which shows 88% sequence identity to EII, a hybrid protein (named Hyb-24) of EII and EII′ was overexpressed, purified and crystallized using the sitting-drop vapour-diffusion method with ammonium sulfate as a precipitant in MES buffer pH 6.5. The crystal belongs to space group P3121 or P3221, with unit-cell parameters a = b = 96.37, c = 113.09 Å. Diffraction data were collected from native and methylmercuric chloride derivative crystals to resolutions of 1.75 and 1.80 Å, respectively.
6-aminohexanoate-dimer hydrolase; biodegradation; nylon oligomer
A ternary complex of the proteinase inhibitor (BTCI) with trypsin and chymotrypsin was crystallized and its crystal structure was solved by molecular replacement.
A ternary complex of the black-eyed pea trypsin and chymotrypsin inhibitor (BTCI) with trypsin and chymotrypsin was crystallized by the sitting-drop vapour-diffusion method with 0.1 M HEPES pH 7.5, 10%(w/v) polyethylene glycol 6000 and 5%(v/v) 2-methyl-2,4-pentanediol as precipitant. BTCI is a small protein with 83 amino-acid residues isolated from Vigna unguiculata seeds and is able to inhibit trypsin and chymotrypsin simultaneously by forming a stable ternary complex. X-ray data were collected from a single crystal of the trypsin–BTCI–chymotrypsin ternary complex to 2.7 Å resolution under cryogenic conditions. The structure of the ternary complex was solved by molecular replacement using the crystal structures of the BTCI–trypsin binary complex (PDB code 2g81) and chymotrypsin (PDB code 4cha) as search models.
proteinase inhibitors; Bowman–Birk inhibitors