8h8s
Bovine Heart Cytochrome c Oxidase in the Calcium-bound Fully Reduced StateBovine Heart Cytochrome c Oxidase in the Calcium-bound Fully Reduced State
Structural highlights
FunctionCOX1_BOVIN 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. Publication Abstract from PubMedThe crystal structure of bovine cytochrome c oxidase (CcO) shows a sodium ion (Na(+)) bound to the surface of subunit I. Changes in the absorption spectrum of heme a caused by calcium ions (Ca(2+)) are detected as small red shifts, and inhibition of enzymatic activity under low turnover conditions is observed by addition of Ca(2+) in a competitive manner with Na(+). In this study, we determined the crystal structure of Ca(2+)-bound bovine CcO in the oxidized and reduced states at 1.7 A resolution. Although Ca(2+) and Na(+) bound to the same site of oxidized and reduced CcO, they led to different coordination geometries. Replacement of Na(+) with Ca(2+) caused a small structural change in the loop segments near the heme a propionate and formyl groups, resulting in spectral changes in heme a. Redox-coupled structural changes observed in the Ca(2+)-bound form were the same as those previously observed in the Na(+)-bound form, suggesting that binding of Ca(2+) does not severely affect enzymatic function, which depends on these structural changes. The relation between the Ca(2+) binding and the inhibitory effect during slow turnover, as well as the possible role of bound Ca(2+) are discussed. Calcium-bound structure of bovine cytochrome c oxidase.,Muramoto K, Shinzawa-Itoh K Biochim Biophys Acta Bioenerg. 2023 Apr 1;1864(2):148956. doi: , 10.1016/j.bbabio.2023.148956. Epub 2023 Jan 25. PMID:36708913[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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