The disulfide oxidoreductase SdbA is active in Streptococcus gordonii using a single C‐terminal cysteine of the CXXC motif. Issue 2 (30th October 2015)

• Record Type: Journal Article
• Authors: Davey, Lauren; Cohen, Alejandro; LeBlanc, Jason; Halperin, Scott A.; Lee, Song F.
• Is Part Of: Molecular microbiology. Volume 99:Issue 2(2016)
• Page Start: 236
• Page End: 253
• Publication Date: 2015-10-30
• Subjects: Molecular microbiology -- Periodicals; 572.829
• DOI: 10.1111/mmi.13227
• Languages: English
• ISSNs: 0950-382X

Abstract

Summary: Recently, we identified a novel disulfide oxidoreductase, SdbA, in the oral bacterium S treptococcus gordonii . Disulfide oxidoreductases form disulfide bonds in nascent proteins using a CXXC catalytic motif. Typically, the N‐terminal cysteine interacts with substrates, whereas the C‐terminal cysteine is buried and only reacts with the first cysteine of the motif. In this study, we investigated the SdbA C 86 P 87 D 88 C 89 catalytic motif. In vitro, SdbA single cysteine variants at the N or C‐terminal position (SdbAC86P and SdbAC89A ) were active but displayed different susceptibility to oxidation, and N‐terminal cysteine was prone to sulfenylation. In S . gordonii, mutants with a single N‐terminal cysteine were inactive and formed unstable disulfide adducts with other proteins. Activity was partially restored by inactivation of pyruvate oxidase, a hydrogen peroxide generator. Presence of the C‐terminal cysteine alone (in the SdbAC86P variant) could complement the Δ sdb A mutant and restore disulfide bond formation in recombinant and natural protein substrates. These results provide evidence that certain disulfide oxidoreductases can catalyze disulfide bond formation using a single cysteine of the CXXC motif, including the buried C‐terminal cysteine. Abstract : Thiol‐disulfide oxidoreductases form disulfide bonds in secreted proteins using a CXXC catalytic motif. Investigation of Streptococcus gordonii oxidoreductase SdbA revealed that the enzyme could function using a single cysteine of the active site. Although the N‐terminal cysteine was prone to oxidation that rendered it inactive, the C‐terminal cysteine was sufficient to sustain catalytic activity.