Adaptation of aerobic respiration to low O-2 environments

作者：Han Huazhi; Hemp James^*; Pace Laura A; Ouyang Hanlin; Ganesan Krithika; Roh Jung Hyeob; Daldal Fevzi; Blanke Steven R; Gennis Robert B

来源：Proceedings of the National Academy of Sciences, 2011, 108(34): 14109-14114.

DOI：10.1073/pnas.1018958108

• cytochrome oxidase
• evolution

Aerobic respiration in bacteria, Archaea, and mitochondria is performed by oxygen reductase members of the heme-copper oxidoreductase superfamily. These enzymes are redox-driven proton pumps which conserve part of the free energy released from oxygen reduction to generate a proton motive force. The oxygen reductases can be divided into three main families based on evolutionary and structural analyses (A-, B-and C-families), with the B-and C-families evolving after the A-family. The A-family utilizes two proton input channels to transfer protons for pumping and chemistry, whereas the B-and C-families require only one. Generally, the B- and C-families also have higher apparent oxygen affinities than the A-family. Here we use whole cell proton pumping measurements to demonstrate differential proton pumping efficiencies between representatives of the A-, B-, and C-oxygen reductase families. The A-family has a coupling stoichiometry of 1 H+/e(-), whereas the B- and C-families have coupling stoichiometries of 0.5 H+/e(-). The differential proton pumping stoichiometries, along with differences in the structures of the proton-conducting channels, place critical constraints on models of the mechanism of proton pumping. Most significantly, it is proposed that the adaptation of aerobic respiration to low oxygen environments resulted in a concomitant reduction in energy conservation efficiency, with important physiological and ecological consequences.

• 出版日期2011-8-23