REVIEW: Investigation of the Mechanism of Membrane Potential Generation by Heme-Copper Respiratory Oxidases in a Real Time Mode

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Sergei A. Siletsky^a

Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia

Received June 29, 2023; Revised August 15, 2023; Accepted August 15, 2023

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Heme-copper respiratory oxidases are highly efficient molecular machines. These membrane enzymes catalyze the final step of cellular respiration in eukaryotes and many prokaryotes: the transfer of electrons from cytochromes or quinols to molecular oxygen and oxygen reduction to water. The free energy released in this redox reaction is converted by heme-copper respiratory oxidases into the transmembrane gradient of the electrochemical potential of hydrogen ions _H+). Heme-copper respiratory oxidases have a unique mechanism for generating H⁺, namely, a redox-coupled proton pump. A combination of direct electrometric method for measuring the kinetics of membrane potential generation with the methods of prestationary kinetics and site-directed mutagenesis in the studies of heme-copper oxidases allows to obtain a unique information on the translocation of protons inside the proteins in real time. The review summarizes the data of studies employing time-resolved electrometry to decipher the mechanisms of functioning of these important bioenergetic enzymes.

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KEY WORDS: bioenergetics, cytochrome oxidase, proteoliposomes, electrogenic proton transfer, generation, proton pump, photoreduction, cytochrome aa₃, kinetics, direct electrometric method, capacitive potentiometry, time resolution, zinc ions

DOI: 10.1134/S0006297923100085

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