title: The heme groups of cytochrome o from Escherichia coli.
abstract: Cytochrome o, one of the two terminal ubiquinol oxidases of Escherichia coli, is structurally and functionally related to cytochrome c oxidase of mitochondria and some bacteria. It has two heme groups, one of which binds CO and forms a binuclear oxygen reaction center with copper. The other heme is unreactive toward ligands, exhibits strong interactions with the binuclear center, and is mainly responsible for the reduced-minus-oxidized alpha band. Protoheme has been thought to be the prosthetic group of b-type cytochromes, including cytochrome o. However, the hemes of cytochrome o are of a different kind, for which we propose the name heme O. Its pyridine hemochrome spectrum is blue-shifted by 4 nm relative to that of protoheme, and chromatographic behavior showed that it is much more hydrophobic than protoheme. Fast atom bombardment mass spectrometry yielded a molecular mass of 839 Da. Heme O is proposed to be a heme A-like molecule, containing a 17-carbon hydroxyethylfarnesyl side chain, but with a methyl residue replacing the formyl group.
authors.affiliation: Department of Medical Chemistry, University of Helsinki, Finland.
authors.forename: A
authors.initials: A
authors.lastname: Puustinen
authors.forename: M
authors.initials: M
authors.lastname: Wikström
mesh_terms: D002248:Carbon Monoxide / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D003573:Cytochrome b Group; D003580:Cytochromes / Q000737:chemistry / Q000378:metabolism*; D004227:Dithionite / Q000494:pharmacology; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D006418:Heme / Q000032:analysis*; D010084:Oxidation-Reduction; D013053:Spectrophotometry
chemical_list: D003573:Cytochrome b Group; D003580:Cytochromes; D029968:Escherichia coli Proteins; C069808:heme O; D004227:Dithionite; D006418:Heme; D002248:Carbon Monoxide; C017168:cytochrome bo, E coli