title: Multiple phosphorylations of cytochrome c oxidase and their functions.
abstract: Cytochrome c oxidase (COX), the terminal enzyme of the mitochondrial electron transport chain, is regulated by isozyme expression, allosteric effectors such as the ATP/ADP ratio, and reversible phosphorylation. Of particular interest is the "allosteric ATP-inhibition," which has been hypothesized to keep the mitochondrial membrane potential at low healthy values (<140 mV), thus preventing the formation of superoxide radical anions, which have been implicated in multiple degenerative diseases. It has been proposed that the "allosteric ATP-inhibition" is switched on by the protein kinase A-dependent phosphorylation of COX. The goal of this study was to identify the phosphorylation site(s) involved in the "allosteric ATP-inhibition" of COX. We report the mass spectrometric identification of four new phosphorylation sites in bovine heart COX. The identified phosphorylation sites include Tyr-218 in subunit II, Ser-1 in subunit Va, Ser-2 in subunit Vb, and Ser-1 in subunit VIIc. With the exception of Ser-2 in subunit Vb, the identified phosphorylation sites were found in enzyme samples with and without "allosteric ATP inhibition," making Ser-2 of subunit Vb a candidate site enabling allosteric regulation. We therefore hypothesize that additional phosphorylation(s) may be required for the "allosteric ATP-inhibition," and that these sites may be easily dephosphorylated or difficult to identify by mass spectrometry.
authors.affiliation: Medizinisches Proteom-Center, Funktionelle Proteomik, Ruhr-Universität Bochum, Bochum, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Helling
authors.forename: Maik
authors.initials: M
authors.lastname: Hüttemann
authors.forename: Rabia
authors.initials: R
authors.lastname: Ramzan
authors.forename: Su Hyeon
authors.initials: SH
authors.lastname: Kim
authors.forename: Icksoo
authors.initials: I
authors.lastname: Lee
authors.forename: Thorsten
authors.initials: T
authors.lastname: Müller
authors.forename: Elmar
authors.initials: E
authors.lastname: Langenfeld
authors.forename: Helmut E
authors.initials: HE
authors.lastname: Meyer
authors.forename: Bernhard
authors.initials: B
authors.lastname: Kadenbach
authors.forename: Sebastian
authors.initials: S
authors.lastname: Vogt
authors.forename: Katrin
authors.initials: K
authors.lastname: Marcus
mesh_terms: D000494:Allosteric Regulation; D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D003576:Electron Transport Complex IV / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D009206:Myocardium / Q000201:enzymology; D010748:Phosphopeptides / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D053719:Tandem Mass Spectrometry
chemical_list: D010748:Phosphopeptides; D021122:Protein Subunits; D003576:Electron Transport Complex IV