Specific enzymic cleavage of polypeptides at cysteine residues.
A method has been developed for specific enzymic cleavage of polypeptides at the N-terminal side of modified cysteine residues. Lysine residues are blocked by trifluoroacetylation and cysteine residues subsequently converted to the 2-aminoethyl derivatives. Digestion of the modified polypeptide with the lysine-specific protease from Armillaria mellea (patented by Walton et al., 1972) occurs only at 2-aminoethylcysteine residues. With the beta chain of human haemoglobin, which contains 2 cysteine and 11 lysine residues, cleavage was observed at both modified cysteines but at none of the lysines. In the case of a polypeptide from bee venom which contains 4 half-cystine and 5 lysine residues, cleavage occurred at only 2 of the modified cysteines and also at 2 lysine residues. The pattern of cleavage in the latter case can be interpreted in terms of the amino acid sequence of the polypeptide.
D000595:Amino Acid Sequence; D000818:Animals; D001516:Bees / Q000201:enzymology; D003545:Cysteine / Q000032:analysis*; D006454:Hemoglobins / Q000032:analysis; D008722:Methods; D010446:Peptide Fragments / Q000032:analysis; D010447:Peptide Hydrolases; D010455:Peptides / Q000032:analysis*; D014269:Trifluoroacetic Acid
D006454:Hemoglobins; D010446:Peptide Fragments; D010455:Peptides; D014269:Trifluoroacetic Acid; D010447:Peptide Hydrolases; D003545:Cysteine