PRIMARY STRUCTURE OF LOBSTER‐MUSCLE ARGININE KINASE: Amino and Carboxyl‐terminal Structure of the Enzyme and Complete Alignment of the Cyanogen‐Bromide Peptides

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Abstract
The acetylation state of the blocked NH2-terminal end of arginine kinase was characterized by the occurrence of 1 mol acetyl group/mol protein; a 5-residue segment corresponding to the amino-terminal portion was isolated from a pronase digestion of the enzyme, and its amino acid sequence determined as N-acetyl Ala-Asx-Ala-Ala-Thr. Arginine kinase is terminated at the carboxyl end by the sequence Lys-Glu-MetOH; this particular 3-residue sequence is repeated 3 times in the overall structure of the protein and is present in 3 CNBr fragments. A peptide of 14 amino acid residues was identified and its amino acid sequence was localized at the COHO-terminal end of the enzyme. The alignment of the 8 CNBr-fragments, which constitute the arginine kinase molecule, was established according to the sequential and compositional properties of 7 unique, tryptic methionyl peptides isolated from the whole protein.