Thermitase from Thermoactinomyces vulgaris; amino acid sequence of the large N-terminal cyanogen bromide peptide

Abstract

The large cyanogen bromide fragment (CB1) represents the N-terminal part of the molecule of thermitase and contains 226 amino acid residues. Its molecular weight calculated from sequential data is 22 932 (the C-terminal residue is regarded as a methionine residue in the calculations). The amino acid sequence of fragment CB1 was determined by analysis of peptides obtained by tryptic hydrolysis of the fragment; these data were complemented by sequence analysis of the chymotryptic digest of fragment Mf (residues 75 through 226) and of chymotryptic fragment ET3 (residues 103 through 226) isolated from the limited tryptic digest of fragment CB1. The peptides were purified by high performance liquid chromatography and by thin layer techniques. The sequence analysis of the large peptides was effected in the sequenator, small peptides were sequenced manually by the DABITC/PITC double coupling technique. The results obtained in this study together with those of previous work5 permitted the complete amino acid sequence of fragment CB1 to be determined.