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1.  Expression, purification, crystallization and preliminary X-ray crystallographic data from TktA, a transketolase from the lactic acid bacterium Lactobacillus salivarius  
Purified transketolase from L. salivarius has been crystallized using the vapour-diffusion technique.
The enzyme transketolase from the lactic acid bacterium Lactobacillus salivarius (subsp. salivarius UCC118) has been recombinantly expressed and purified using an Escherichia coli expression system. Purified transketolase from L. salivarius has been crystallized using the vapour-diffusion technique. The crystals belonged to the trigonal space group P3221, with unit-cell parameters a = b = 75.43, c = 184.11 Å, and showed diffraction to 2.3 Å resolution.
PMCID: PMC2917285  PMID: 20693662
TktA; transketolases; Lactobacillus salivarius
2.  Useable diffraction data from a multiple microdomain-containing crystal of Ascaris suum As-p18 fatty-acid-binding protein using a microfocus beamline 
As-p18, an unusual fatty-acid-binding protein from a parasitic nematode, was expressed in bacteria, purified and crystallized. The use of a microfocus beamline was essential for data collection.
As-p18 is a fatty-acid-binding protein from the parasitic nematode Ascaris suum. Although it exhibits sequence similarity to mammalian intracellular fatty-acid-binding proteins, it contains features that are unique to nematodes. Crystals were obtained, but initial diffraction data analysis revealed that they were composed of a number of ‘microdomains’. Interpretable data could only be collected using a microfocus beamline with a beam size of 12 × 8 µm.
PMCID: PMC3412778  PMID: 22869127
fatty-acid-binding proteins; parasitic nematodes; Ascaris suum; microfocus beamlines
3.  Outer Membrane Protein A of Bovine and Ovine Isolates of Mannheimia haemolytica Is Surface Exposed and Contains Host Species-Specific Epitopes ▿  
Infection and Immunity  2011;79(11):4332-4341.
Mannheimia haemolytica is the etiological agent of pneumonic pasteurellosis of cattle and sheep; two different OmpA subclasses, OmpA1 and OmpA2, are associated with bovine and ovine isolates, respectively. These proteins differ at the distal ends of four external loops, are involved in adherence, and are likely to play important roles in host adaptation. M. haemolytica is surrounded by a polysaccharide capsule, and the degree of OmpA surface exposure is unknown. To investigate surface exposure and immune specificity of OmpA among bovine and ovine M. haemolytica isolates, recombinant proteins representing the transmembrane domain of OmpA from a bovine serotype A1 isolate (rOmpA1) and an ovine serotype A2 isolate (rOmpA2) were overexpressed, purified, and used to generate anti-rOmpA1 and anti-rOmpA2 antibodies, respectively. Immunogold electron microscopy and immunofluorescence techniques demonstrated that OmpA1 and OmpA2 are surface exposed, and are not masked by the polysaccharide capsule, in a selection of M. haemolytica isolates of various serotypes and grown under different growth conditions. To explore epitope specificity, anti-rOmpA1 and anti-rOmpA2 antibodies were cross-absorbed with the heterologous isolate to remove cross-reacting antibodies. These cross-absorbed antibodies were highly specific and recognized only the OmpA protein of the homologous isolate in Western blot assays. A wider examination of the binding specificities of these antibodies for M. haemolytica isolates representing different OmpA subclasses revealed that cross-absorbed anti-rOmpA1 antibodies recognized OmpA1-type proteins but not OmpA2-type proteins; conversely, cross-absorbed anti-rOmpA2 antibodies recognized OmpA2-type proteins but not OmpA1-type proteins. Our results demonstrate that OmpA1 and OmpA2 are surface exposed and could potentially bind to different receptors in cattle and sheep.
PMCID: PMC3257919  PMID: 21896777
4.  Crystallization and preliminary structural studies of champedak galactose-binding lectin 
Galactose-binding lectin from champedak was crystallized at 293 K. Preliminary X-ray diffraction analyses are reported.
Galactose-binding lectin from champedak (Artocarpus integer) consists of two chains: α and β (133 and 21 amino acids, respectively). It has been shown to recognize and bind to carbohydrates involved in IgA and C1 inhibitor molecules. The protein was purified and crystallized at 293 K. Crystals were observed in two space groups, P21 and P21212, and diffracted to 1.65 and 2.6 Å, respectively.
PMCID: PMC2795594  PMID: 19724126
lectins; Artocarpus integer; champedak; galactose binding
5.  Purification, crystallization and preliminary X-ray diffraction analysis of RafE, a sugar-binding lipoprotein from Streptococcus pneumoniae  
The mature form of RafE has been expressed, purified and crystallized. X-ray diffraction data have been collected to 3.65 and 2.90 Å resolution from native and selenomethionine-derivative crystals, respectively.
Streptococcus pneumoniae contains a large number of sugar-transport systems and the system responsible for raffinose uptake has recently been identified. The substrate-binding protein component of this system shares strong sequence homology with the multiple sugar metabolism substrate-binding protein MsmE from S. mutans and contains a lipoprotein-attachment site at cysteine residue 23. A truncated form (residues 24–419) of RafE from S. pneumoniae was cloned and overexpressed in Escherichia coli. Native and selenomethionine-labelled protein have been crystallized in the hexagonal space group P6122. Diffraction data have been successfully phased to 2.90 Å using Se SAD data and model building is in progress.
PMCID: PMC2242947  PMID: 16820692
SP1897; RafE; raffinose; ABC transporter; selenomethionine; SAD
6.  Innate Immune Defense against Pneumococcal Pneumonia Requires Pulmonary Complement Component C3  
Infection and Immunity  2005;73(7):4245-4252.
Complement is known to be involved in protection against systemic infection with Streptococcus pneumoniae. However, less is known about effects of complement within the lungs during pneumococcal pneumonia. By intranasally infecting transgenic mice unable to express complement C3, we investigated the role of complement in pulmonary defenses against S. pneumoniae. It was demonstrated that within the lungs, there is a requirement for C3 during the initial hours of infection. It was found that within 1 h of infection, bacterial loads decreased within lung airways of control mice as C3 protein increased. The lack of C3 resulted in the inability to control growth of wild-type or attenuated pneumococci within the lungs and bloodstream, resulting in an overwhelming inflammatory response and shorter survival times. Our results show that during the initial hours of infection with S. pneumoniae, C3 is protective within the lungs and subsequently plays an important role systemically.
PMCID: PMC1168602  PMID: 15972516
7.  Crystal Structure of the Response Regulator 02 Receiver Domain, the Essential YycF Two-Component System of Streptococcus pneumoniae in both Complexed and Native States† 
Journal of Bacteriology  2004;186(9):2872-2879.
A variety of bacterial cellular responses to environmental signals are mediated by two-component signal transduction systems comprising a membrane-associated histidine protein kinase and a cytoplasmic response regulator (RR), which interpret specific stimuli and produce a measured physiological response. In RR activation, transient phosphorylation of a highly conserved aspartic acid residue drives the conformation changes needed for full activation of the protein. Sequence homology reveals that RR02 from Streptococcus pneumoniae belongs to the OmpR subfamily of RRs. The structures of the receiver domains from four members of this family, DrrB and DrrD from Thermotoga maritima, PhoB from Escherichia coli, and PhoP from Bacillus subtilis, have been elucidated. These domains are globally very similar in that they are composed of a doubly wound α5β5; however, they differ remarkably in the fine detail of the β4-α4 and α4 regions. The structures presented here reveal a further difference of the geometry in this region. RR02 is has been shown to be the essential RR in the gram-positive bacterium S. pneumoniae R. Lange, C. Wagner, A. de Saizieu, N. Flint, J. Molnos, M. Stieger, P. Caspers, M. Kamber, W. Keck, and K. E. Amrein, Gene 237:223-234, 1999; J. P. Throup, K. K. Koretke, A. P. Bryant, K. A. Ingraham, A. F. Chalker, Y. Ge, A. Marra, N. G. Wallis, J. R. Brown, D. J. Holmes, M. Rosenberg, and M. K. Burnham, Mol. Microbiol. 35:566-576, 2000). RR02 functions as part of a phosphotransfer system that ultimately controls the levels of competence within the bacteria. Here we report the native structure of the receiver domain of RR02 from serotype 4 S. pneumoniae (as well as acetate- and phosphate-bound forms) at different pH levels. Two native structures at 2.3 Å, phased by single-wavelength anomalous diffraction (xenon SAD), and 1.85 Å and a third structure at pH 5.9 revealed the presence of a phosphate ion outside the active site. The fourth structure revealed the presence of an acetate molecule in the active site.
PMCID: PMC387779  PMID: 15090529

Results 1-7 (7)