期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1991
卷号：88
期号：14
页码：6122-6126
DOI：10.1073/pnas.88.14.6122
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：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.
