Structure/function of oxygen-regulated isoforms in cytochrome c oxidase.

摘要: Eukaryotic cytochrome c oxidases are complex oligomeric membrane proteins composed of subunit polypeptides encoded by both nuclear and mitochondrial genomes. While the mitochondrially subunits unique genes, some nuclear-encoded multigene families. The isoforms produced these families tissue-specific and/or developmentally regulated in mammals environmentally lower eukaryotes. Isoforms for one subunits, V, yeast Saccharomyces cerevisiae VII, slime mold Dictyostelium discoideum differentially oxygen concentration. Extensive studies with V have revealed that genes switched on or off at very low concentrations (0.5-1 micromol l-1 O2) they affect catalytic properties holocytochrome oxidase differentially. By altering an internal step electron transfer between heme a binuclear reaction center (composed a3 CuB), 'hypoxic' isoform, Vb, enhances constant three- to fourfold relative 'aerobic' Va. Modeling suggest this occurs interaction transmembrane helix VII I V. inverse regulation two allows cells assemble different types holoenzyme isoenzymes response Oxygen also regulates level transcription other nuclear-coded affects (I II) post-transcriptionally. Thus, activity is tensions determined part number molecules assembled oxygen-regulated possibility type control exists organisms considered.