Poly(ADP-ribose) polymerase from Ehrlich ascites-tumour cells. Amino acid composition, N-terminal analysis and chemical cleavage of the purified protein.

Poly(ADP-ribose) polymerase was purified from Ehrlich ascites-tumour cells by two novel methods. Analysis for amino acid composition revealed a high percentage of acidic amino acids or their amides, and of basic amino acids. N-Terminal analysis with dansyl chloride revealed no terminal amino acid, indicating a blocked N-terminal amino group. Analysis by gel electrophoresis of protein treated with 3-bromo-3-methyl-2-(2-nitrophenylthio)-3H-indole, under conditions where selective cleavage of the polypeptide chain at tryptophan residues is obtained, showed six major peptide bands.