title: Subunit IV of human cytochrome c oxidase, polymorphism and a putative isoform.
abstract: As part of our study of isoenzyme forms of human cytochrome c oxidase, we purified subunit IV from human heart and skeletal muscle with reversed-phase HPLC and determined the N-terminal amino acid sequences and the electrophoretic mobility. The N-terminus of human heart subunit IV proved to be ragged with 30% of the protein lacking the first three residues. Also a Tyr/Phe polymorphism was observed at residue 16. No differences in N-terminal sequence and electrophoretic mobility were observed between subunit IV of cytochrome c oxidase from human heart and skeletal muscle. Therefore, our results suggest that identical subunits IV are present in cytochrome c oxidase from human heart and skeletal muscle. A putative isoform of subunit IV with a blocked N-terminus was purified from human heart cytochrome c oxidase, which proved to have a different retention time on a reversed-phase column and also a slightly higher electrophoretic mobility on an SDS-polyacrylamide gel compared to the native subunit IV. We could not demonstrate the existence of isoforms of subunit IV in human skeletal muscle.
authors.affiliation: E.C. Slater Institute for Biochemical Research, University of Amsterdam, The Netherlands.
authors.forename: A B
authors.initials: AB
authors.lastname: Van Kuilenburg
authors.forename: J J
authors.initials: JJ
authors.lastname: Van Beeumen
authors.forename: H
authors.initials: H
authors.lastname: Demol
authors.forename: C
authors.initials: C
authors.lastname: Van den Bogert
authors.forename: I
authors.initials: I
authors.lastname: Schouten
authors.forename: A O
authors.initials: AO
authors.lastname: Muijsers
mesh_terms: D000595:Amino Acid Sequence; D003576:Electron Transport Complex IV / Q000737:chemistry* / Q000302:isolation & purification; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D009132:Muscles / Q000201:enzymology*; D009206:Myocardium / Q000201:enzymology*
chemical_list: D007527:Isoenzymes; D003576:Electron Transport Complex IV