On the structure of sperm whale myoglobin: I. The amino acid composition and terminal groups of the chromatographically purified protein

Abstract

The hemoprotein that comprises 96% by weight of the protein in crystalline sperm whale myoglobin may be resolved into at least five components by chromatography on the carboxylic resin IRC-50. Four of the five heme-containing components (representing 92% of the protein) possess identical amino acid compositions; the fifth component has not been obtained free of non-heme protein but appears to be very similar to, if not identical with, the composition of the other heme-containing components. The amino acid analyses have shown that the myoglobin molecule contains 153 amino acid residues and possesses a molecular weight of 17,816. Sixty-five per cent of the heme-containing protein is represented by two of the components, designated as components TV and V, and these have been isolated in quantity for structural study. Quantitative methods have been used to demonstrate that components IV and V of sperm whale myoglobin contain a single polypeptide chain with valine at the amino-terminus and glutamine at the carboxyl-terminus.