[COX1_RHOSH] Cytochrome c oxidase is the component of the respiratory chain that catalyzes the reduction of oxygen to water. Subunits 1-3 form the functional core of the enzyme complex. Co I is the catalytic subunit of the enzyme. Electrons originating in cytochrome c are transferred via the copper A center of subunit 2 and heme a of subunit 1 to the bimetallic center formed by heme a3 and copper B. This cytochrome c oxidase shows proton pump activity across the membrane in addition to the electron transfer. [COX2_RHOSH] Subunits I and II form the functional core of the enzyme complex. Electrons originating in cytochrome c are transferred via heme a and Cu(A) to the binuclear center formed by heme a3 and Cu(B).
Evolutionary Conservation
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Publication Abstract from PubMed
A role for conformational change in the coupling mechanism of cytochrome c oxidase is the subject of controversy. Relatively small conformational changes have been reported in comparisons of reduced and oxidized crystal structures of bovine oxidase but none in bacterial oxidases. Comparing the X-ray crystal structures of the reduced (at 2.15 A resolution) and oxidized forms of cytochrome c oxidase from Rhodobacter sphaeroides, we observe a displacement of heme a(3) involving both the porphyrin ring and the hydroxyl farnesyl tail, accompanied by protein movements in nearby regions, including the mid part of helix VIII of subunit I which harbors key residues of the K proton uptake path, K362 and T359. The conformational changes in the reduced form are reversible upon reoxidation. They result in an opening of the top of the K pathway and more ordered waters being resolved in that region, suggesting an access path for protons into the active site. In all high-resolution structures of oxidized R. sphaeroides cytochrome c oxidase, a water molecule is observed in the hydrophobic region above the top of the D path, strategically positioned to facilitate the connection of residue E286 of subunit I to the active site or to the proton pumping exit path. In the reduced and reduced plus cyanide structures, this water molecule disappears, implying disruption of proton conduction from the D path under conditions when the K path is open, thus providing a mechanism for alternating access to the active site.
Redox-dependent conformational changes in cytochrome C oxidase suggest a gating mechanism for proton uptake.,Qin L, Liu J, Mills DA, Proshlyakov DA, Hiser C, Ferguson-Miller S Biochemistry. 2009 Jun 16;48(23):5121-30. PMID:19397279[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
↑Qin L, Liu J, Mills DA, Proshlyakov DA, Hiser C, Ferguson-Miller S. Redox-dependent conformational changes in cytochrome C oxidase suggest a gating mechanism for proton uptake. Biochemistry. 2009 Jun 16;48(23):5121-30. PMID:19397279 doi:10.1021/bi9001387
