Studies on cytochrome c oxidase, X. Isolation and amino-acid sequence of polypeptide VIIIb.
The isolation and sequence determination of the cytoplasmically synthesized polypeptide VIIIb from beef heart cytochrome c oxidase is described. Several methods for isolating polypeptide VIIIb with gelchromatographic technics are presented. The complete amino-acid sequence is deduced from a N-terminal sequencer run, overlapping tryptic peptides and peptides obtained after tryptophan specific cleavage with cyanogen bromide in heptafluorobutyric acid/formic acid. The small protein consists of 46 amino acids and has a molecular mass of 4 962 Da. The existence of a hydrophobic segment with a length of 20 residues characterizes it as a membrane penetrating protein. The stoichiometry of this polypeptide in the functional monomer of cytochrome c oxidase (complex IV) is 2 and is thus different from all the other polypeptides constituting the respiratory complex IV. The function of this component of the terminal oxidase is as yet unknown.
D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D003576:Electron Transport Complex IV / Q000302:isolation & purification*; D009206:Myocardium / Q000201:enzymology; D010446:Peptide Fragments / Q000032:analysis; D010455:Peptides / Q000302:isolation & purification; D013816:Thermodynamics; D014357:Trypsin
D010446:Peptide Fragments; D010455:Peptides; D003576:Electron Transport Complex IV; D014357:Trypsin