Roles of a conserved arginine residue of DsbB in linking protein disulfide-bond-formation pathway to the respiratory chain of Escherichia coli
AUTOR(ES)
Kadokura, Hiroshi
FONTE
The National Academy of Sciences
RESUMO
The active-site cysteines of DsbA, the periplasmic disulfide-bond-forming enzyme of Escherichia coli, are kept oxidized by the cytoplasmic membrane protein DsbB. DsbB, in turn, is oxidized by two kinds of quinones (ubiquinone for aerobic and menaquinone for anaerobic growth) in the electron-transport chain. We describe the isolation of dsbB missense mutations that change a highly conserved arginine residue at position 48 to histidine or cysteine. In these mutants, DsbB functions reasonably well aerobically but poorly anaerobically. Consistent with this conditional phenotype, purified R48H exhibits very low activity with menaquinone and an apparent Michaelis constant (Km) for ubiquinone seven times greater than that of the wild-type DsbB, while keeping an apparent Km for DsbA similar to that of wild-type enzyme. From these results, we propose that this highly conserved arginine residue of DsbB plays an important role in the catalysis of disulfide bond formation through its role in the interaction of DsbB with quinones.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=27118Documentos Relacionados
- Evidence that the pathway of disulfide bond formation in Escherichia coli involves interactions between the cysteines of DsbB and DsbA.
- Respiratory chain is required to maintain oxidized states of the DsbA-DsbB disulfide bond formation system in aerobically growing Escherichia coli cells
- Two cysteines in each periplasmic domain of the membrane protein DsbB are required for its function in protein disulfide bond formation.
- Mutational Analysis of the Disulfide Catalysts DsbA and DsbB
- Paradoxical redox properties of DsbB and DsbA in the protein disulfide-introducing reaction cascade