Studies on CytochromecOxidase, IX. The Primary Structure of Polypeptide VI

Abstract

The complete amino acid sequence of the cytoplasmic polypeptide VIa of cytochrome c oxidase from beef heart is described. The primary structure of this component of complex IV of the respiratory chain is elucidated by isolation and sequencing of overlapping glutamic acid, arginine, tryptophan and methionine fragements obtained by cleavage with Staphylococcus aureus protease, protease from submaxillary glands of mice, 2-iodosylbenzoic acid and cyanogen bromide. The chain length of polypeptide VIa is 98 amino acids, the resulting molecular mass 10670 daltons. The hydrophilic protein does not contain a hydrophobic membrane penetrating sequence domain. Its function in the respiratory complex IV is unknown.