Regulation of cytochrome c oxidase activity by modulation of the catalytic site.

ABSTRACT: The respiratory supercomplex factor 1 (Rcf 1) in Saccharomyces cerevisiae binds to intact cytochrome c oxidase (CytcO) and has also been suggested to be an assembly factor of the enzyme. Here, we isolated CytcO from rcf1? mitochondria using affinity chromatography and investigated reduction, inter-heme electron transfer and ligand binding to heme a₃. The data show that removal of Rcf1 yields two CytcO sub-populations. One of these sub-populations exhibits the same functional behavior as CytcO isolated from the wild-type strain, which indicates that intact CytcO is assembled also without Rcf1. In the other sub-population, which was shown previously to display decreased activity and accelerated ligand-binding kinetics, the midpoint potential of the catalytic site was lowered. The lower midpoint potential allowed us to selectively reduce one of the two sub-populations of the rcf1? CytcO, which made it possible to investigate the functional behavior of the two CytcO forms separately. We speculate that these functional alterations reflect a mechanism that regulates O₂ binding and trapping in CytcO, thereby altering energy conservation by the enzyme.

SUBMITTER: Schafer J 

PROVIDER: S-EPMC6065377 | biostudies-literature | 2018 Jul

REPOSITORIES: biostudies-literature