Structural and Biochemical Characterization of Chlamydia trachomatis DsbA Reveals a Cysteine-Rich and Weakly Oxidising Oxidoreductase

• Published in: PloS one 2016-12, Vol.11 (12), p.e0168485-e0168485
• Main Authors: Christensen, Signe, Grøftehauge, Morten K, Byriel, Karl, Huston, Wilhelmina M, Furlong, Emily, Heras, Begoña, Martin, Jennifer L, McMahon, Róisín M
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Antimicrobial agents; Bacteria; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Biochemistry; Biology; Biology and Life Sciences; Catalysis; Catalytic Domain; Chemical bonds; Chlamydia; Chlamydia trachomatis; Chlamydia trachomatis - physiology; Crystal structure; Crystallography, X-Ray; Cysteine - chemistry; Cysteine - metabolism; Cystine; Disulfide bonds; Drugs; E coli; Enterobacteriaceae; Enzymes; Escherichia coli; Genome, Bacterial; Gram-negative bacteria; Homology; Humans; Hydrophobicity; Infertility; Medicine and Health Sciences; Membrane proteins; Models, Molecular; Mycobacterium tuberculosis; Oxidation; Oxidation-Reduction; Oxidoreductase; Oxidoreductases; Oxidoreductases - chemistry; Oxidoreductases - metabolism; Pelvic inflammatory disease; Physical Sciences; Protein C; Protein Conformation; Protein Disulfide-Isomerases - chemistry; Protein Disulfide-Isomerases - metabolism; Protein Folding; Proteins; Redox properties; Research and Analysis Methods; Sequence Homology, Amino Acid; Sexually transmitted diseases; STD; Structural analysis; Structure-function relationships; Trachoma; Tuberculosis; Virulence; Virulence factors
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0168485

The Gram negative bacteria Chlamydia trachomatis is an obligate intracellular human pathogen that can cause pelvic inflammatory disease, infertility and blinding trachoma. C. trachomatis encodes a homolog of the dithiol oxidoreductase DsbA. Bacterial DsbA proteins introduce disulfide bonds to folding proteins providing structural bracing for secreted virulence factors, consequently these proteins are potential targets for antimicrobial drugs. Despite sharing functional and structural characteristics, the DsbA enzymes studied to date vary widely in their redox character. In this study we show that the truncated soluble form of the predicted membrane anchored protein C. trachomatis DsbA (CtDsbA) has oxidase activity and redox properties broadly similar to other characterized DsbA proteins. However CtDsbA is distinguished from other DsbAs by having six cysteines, including a second disulfide bond, and an unusual dipeptide sequence in its catalytic motif (Cys-Ser-Ala-Cys). We report the 2.7 Å crystal structure of CtDsbA revealing a typical DsbA fold, which is most similar to that of DsbA-II type proteins. Consistent with this, the catalytic surface of CtDsbA is negatively charged and lacks the hydrophobic groove found in EcDsbA and DsbAs from other enterobacteriaceae. Biochemical characterization of CtDsbA reveals it to be weakly oxidizing compared to other DsbAs and with only a mildly destabilizing active site disulfide bond. Analysis of the crystal structure suggests that this redox character is consistent with a lack of contributing factors to stabilize the active site nucleophilic thiolate relative to more oxidizing DsbA proteins.