6ci0
From Proteopedia
Catalytic core subunits (I and II) of cytochrome C oxidase from Rhodobacter sphaeroides with E101A (II) mutation
Structural highlights
Function[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). Publication Abstract from PubMedThree mutant forms of Rhodobacter sphaeroides cytochrome c oxidase (RsCcO) were created to test for multiple K-path entry sites (E101W), the existence of an "upper ligand site" (M350W), and the nature and binding specificity of the "lower ligand site" (P315W/E101A) in the region of a crystallographically-defined deoxycholate at the K-path entrance. The effects of inhibitory and stimulatory detergents (dodecyl maltoside and Tween20) on these mutants are presented, as well as competition with other ligands, including the potentially physiologically relevant ligands cholesterol and retinoic acid. Ligands are shown to be able to compete with natural lipids to affect the activity of membrane-bound RsCcO. Results point to a single K-path entrance site at E101, with a single ligand binding pocket proximal to the entrance. The affinity of this pocket for amphipathic ligands is enhanced by removal of the E101 carboxyl and blocked by substituting a tryptophan in this area. A new crystal structure of the E101A mutant of RsCcO is presented that illustrates the structural basis of these results, showing that the loss of the E101 carboxyl creates a more hydrophobic groove consistent with altered ligand affinities. The K-path entrance in cytochrome c oxidase is defined by mutation of E101 and controlled by an adjacent ligand binding domain.,Hiser C, Liu J, Ferguson-Miller S Biochim Biophys Acta. 2018 Apr 4. pii: S0005-2728(18)30060-4. doi:, 10.1016/j.bbabio.2018.03.017. PMID:29626419[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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