title: Crystal structure of the periplasmic disulfide-bond isomerase DsbC from Salmonella enterica serovar Typhimurium and the mechanistic implications.
abstract: The disulfide-bond isomerase DsbC plays a crucial role in the folding of bacterial proteins in the periplasmic space. DsbC has a V-shaped dimeric structure with two domains, and Cys98 in the C-terminal domain attacks inappropriate disulfide bonds in substrate proteins due to its high nucleophilic activity. In this article, we present the crystal structure of DsbC from Salmonella enterica serovar Typhimurium. We evaluated the conserved residues Asp95 and Arg125, which are located close to Cys98. The mutation of Asp95 or Arg125 abolished the disulfide isomerase activity of DsbC in an in vitro assay using a protein substrate, and the R125A mutation significantly reduced the chaperone activity for the substrate RNase I in vivo. Furthermore, a comparative analysis suggested that the conformation of Arg125 varies depending on the packing or protein-protein interactions. Based on these findings, we suggest that Asp95 and Arg125 modulate the pKa of Cys98 during catalysis.
authors.affiliation: Department of Manufacturing Pharmacy and Research Institute for Drug Development, Pusan National University, Busan 609-735, Republic of Korea.
authors.forename: Li
authors.initials: L
authors.lastname: Jiao
authors.forename: Jin-Sik
authors.initials: JS
authors.lastname: Kim
authors.forename: Woo-Seok
authors.initials: WS
authors.lastname: Song
authors.forename: Bo-Young
authors.initials: BY
authors.lastname: Yoon
authors.forename: Kangseok
authors.initials: K
authors.lastname: Lee
authors.forename: Nam-Chul
authors.initials: NC
authors.lastname: Ha
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D019704:Protein Disulfide-Isomerases / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D012486:Salmonella typhimurium / Q000201:enzymology*; D016415:Sequence Alignment; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; D019704:Protein Disulfide-Isomerases
keywords: Catalytic mechanism; Crystal structure; Disulfide isomerase; DsbC; Salmonella; pKa perturbation