Alternative initial proton acceptors for the D pathway of Rhodobacter sphaeroides cytochrome c oxidase.

ABSTRACT: To characterize protein structures that control proton uptake, we assayed forms of cytochrome c oxidase (CcO) containing a carboxyl or a thiol group in line with the initial, internal waters of the D pathway for proton transfer in the presence and absence of subunit III. Subunit III provides approximately half of the protein surrounding the entry region of the D pathway. The N139D/D132N mutant contains a carboxyl group 6 Å within the D pathway and lacks the normal, surface-exposed proton acceptor, Asp-132. With subunit III, the steady-state activity of this mutant is slow, but once subunit III is removed, its activity is the same as that of wild-type CcO lacking subunit III (∼1800 H+/s). Thus, a carboxyl group∼25% within the pathway enhances proton uptake even though the carboxyl has no di

SUBMITTER: Varanasi L 

PROVIDER: S-EPMC3082432 | biostudies-literature | 2011 Apr

REPOSITORIES: biostudies-literature