The Whole Structure of the 13-Subunit Oxidized Cytochrome c Oxidase at 2.8 Å

TLDR

A hydrogen‑bond network links CuA to heme a, and two proton‑pumping pathways spanning the membrane were identified, along with channels for proton transfer, water production/removal, and oxygen transport. The 2.8‑Å crystal structure of bovine heart cytochrome c oxidase shows a 13‑subunit complex with diverse lipids and metal cofactors, and 3560 of its 3606 residues were refined into a reliable model.

Abstract

The crystal structure of bovine heart cytochrome c oxidase at 2.8 Å resolution with an R value of 19.9 percent reveals 13 subunits, each different from the other, five phosphatidyl ethanolamines, three phosphatidyl glycerols and two cholates, two hemes A, and three copper, one magnesium, and one zinc. Of 3606 amino acid residues in the dimer, 3560 have been converged to a reasonable structure by refinement. A hydrogen-bonded system, including a propionate of a heme A (heme a), part of peptide backbone, and an imidazole ligand of Cu A , could provide an electron transfer pathway between Cu A and heme a. Two possible proton pathways for pumping, each spanning from the matrix to the cytosolic surfaces, were identified, including hydrogen bonds, internal cavities likely to contain water molecules, and structures that could form hydrogen bonds with small possible conformational change of amino acid side chains. Possible channels for chemical protons to produce H 2 O, for removing the produced water, and for O 2 , respectively, were identified.