Subunit IV of human cytochrome c oxidase, polymorphism and a putative isoform.
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.
Van Kuilenburg
A B
AB
E.C. Slater Institute for Biochemical Research, University of Amsterdam, The Netherlands.
Van Beeumen
J J
JJ
Demol
H
H
Van den Bogert
C
C
Schouten
I
I
Muijsers
A O
AO
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*
D007527:Isoenzymes; D003576:Electron Transport Complex IV