Structure covalente de la myoglobine de cheval

Abstract

The complete sequence (153 amino acids) of horse heart myoglobin has been established. The sequence of a peptide isolated from chymotrypsin hydrolyzates of globin allowed to fill a gap in the tentative sequence previously proposed; this peptide was studied by means of pepsin hydrolysis, action of N‐bromosuccinimide on histidyl bonds, and Edman degradation method associated with dansylation. After hydrolysis of globin by chymotrypsin treated by TLCK, the same major peptides were found as after hydrolysis by non‐treated chymotrypsin. These peptides were identified by ion‐exchange resins and bidimensional paper chromatography, and also by the determination of their amino‐acid composition. The suppression of secondary cuts explains the presence of new peptides, whose the composition and N‐terminal sequences were determined. It was then possible to confirm several sequences which could be previously deduced from the study of split products after cyanogen bromide treatment. The specificity of chymotrypsin towards certain types of peptide bonds is discussed. Horse myoglobin, as compared with sperm whale myoglobin, contains 18 differences: 17 substitutions and one inversion. The major part of the substitutions are located in N‐ and C‐terminal sequences; they are all punctiform, resulting from the replacement of only one base in each codon. Copyright © 1969, Wiley Blackwell. All rights reserved