5weh
Cytochrome c oxidase from Rhodobacter sphaeroides in the reduced state
Structural highlights
FunctionCOX1_CERSP 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. Publication Abstract from PubMedGiven the central role of cytochrome c oxidase (CcO) in health and disease, it is an increasingly important question as to how the activity and efficiency of this key enzyme are regulated to respond to a variety of metabolic states. The present paper summarizes evidence for two modes of regulation of activity: first, by redox-induced conformational changes involving the K-proton uptake path; and secondly, by ligand binding to a conserved site immediately adjacent to the entrance of the K-path that leads to the active site. Both these phenomena highlight the importance of the K-path in control of CcO. The redox-induced structural changes are seen in both the two-subunit and a new four-subunit crystal structure of bacterial CcO and suggest a gating mechanism to control access of protons to the active site. A conserved ligand-binding site, first discovered as a bile salt/steroid site in bacterial and mammalian oxidases, is observed to bind an array of ligands, including nucleotides, detergents, and other amphipathic molecules. Highly variable effects on activity, seen for these ligands and mutations at the K-path entrance, can be explained by differing abilities to inhibit or stimulate K-path proton uptake by preventing or allowing water organization. A new mutant form in which the K-path is blocked by substituting the conserved carboxyl with a tryptophan clarifies the singularity of the K-path entrance site. Further study in eukaryotic systems will determine the physiological significance and pharmacological potential of ligand binding and conformational change in CcO. Role of conformational change and K-path ligands in controlling cytochrome c oxidase activity.,Liu J, Hiser C, Ferguson-Miller S Biochem Soc Trans. 2017 Aug 24. pii: BST20160138. doi: 10.1042/BST20160138. PMID:28842531[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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