A histidine residue acting as a controlling site for dioxygen reduction and proton pumping by cytochrome c oxidase.

ABSTRACT: Cytochrome c oxidase transfers electrons and protons for dioxygen reduction coupled with proton pumping. These electron and proton transfers are tightly coupled with each other for the effective energy transduction by various unknown mechanisms. Here, we report a coupling mechanism by a histidine (His-503) at the entrance of a proton transfer pathway to the dioxygen reduction site (D-pathway) of bovine heart cytochrome c oxidase. In the reduced state, a water molecule is fixed by hydrogen bonds between His-503 and Asp-91 of the D-pathway and is linked via two water arrays extending to the molecular surface. The microenvironment of Asp-91 appears in the x-ray structure to have a proton affinity as high as that of His-503. Thus, Asp-91 and His-503 cooperatively trap, on the fixed water molec

SUBMITTER: Muramoto K 

PROVIDER: S-EPMC1876541 | biostudies-literature | 2007 May

REPOSITORIES: biostudies-literature