title: Structural and Biochemical Characterization of Chlamydia trachomatis DsbA Reveals a Cysteine-Rich and Weakly Oxidising Oxidoreductase.
abstract: 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.
authors.affiliation: Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, University of Queensland, St. Lucia, Queensland, Australia.
authors.forename: Signe
authors.initials: S
authors.lastname: Christensen
authors.affiliation: Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, University of Queensland, St. Lucia, Queensland, Australia.
authors.forename: Morten K
authors.initials: MK
authors.lastname: Grøftehauge
authors.affiliation: Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, University of Queensland, St. Lucia, Queensland, Australia.
authors.forename: Karl
authors.initials: K
authors.lastname: Byriel
authors.affiliation: School of Life Sciences, University of Technology Sydney, Broadway, New South Wales, Australia.
authors.forename: Wilhelmina M
authors.initials: WM
authors.lastname: Huston
authors.affiliation: Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, University of Queensland, St. Lucia, Queensland, Australia.
authors.forename: Emily
authors.initials: E
authors.lastname: Furlong
authors.affiliation: Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, University of Queensland, St. Lucia, Queensland, Australia.
authors.forename: Begoña
authors.initials: B
authors.lastname: Heras
authors.affiliation: Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, University of Queensland, St. Lucia, Queensland, Australia.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Martin
authors.affiliation: Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, University of Queensland, St. Lucia, Queensland, Australia.
authors.forename: Róisín M
authors.identifier: http://orcid.org/0000-0001-5437-0355
authors.initials: RM
authors.lastname: McMahon
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain; D002692:Chlamydia trachomatis / Q000502:physiology*; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism*; D016680:Genome, Bacterial; D006801:Humans; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D019704:Protein Disulfide-Isomerases / Q000737:chemistry / Q000378:metabolism*; D017510:Protein Folding; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D010088:Oxidoreductases; D019704:Protein Disulfide-Isomerases; D003545:Cysteine