A new redox loop formality involving metal‐catalysed hydroxide‐ion translocation A hypothetical Cu loop mechanism for cytochrome oxidase

Abstract

A new hypothetical type of redox loop is described, which translocates hydroxide ions instead of protons. Conventional protonmotive redox loops use carriers of protons with electrons (e.g. QH₂/Q systems) to couple electron transfer to the translocation of protons. The putative hydroxidemotive redox loop uses carriers of hydroxide ions against electrons (e.g. transition-metal centres) to couple electron transfer to the translocation of hydroxide ions. This simple idea leads to the proposal of a hydroxidemotive Cu loop mechanism that may possibly be applicable to the Cu_A or Cu_B centre of cytochrome oxidase, and might thus account for the coupling of electron transfer to net proton translocation in that osmoenzyme.