Primary Structure of Lobster‐Muscle Arginine Kinase

Abstract

Cleavage of the S ‐carboxymethylated arginine kinase with cyanogen bromide gives rise to eight peptides of 11, 17, 23, 39, 60, 81, 87, 103 amino‐acid residues, one of which is an overlap. Ion‐exchange chromatography on sulfopropyl‐Sephadex and gel filtration on Sephadex G‐50 fine, in urea medium, as well as electrochromatography have been used with success for their separation. Their amino‐acid composition and end‐group structure have been determined and compared to those of the whole protein. All peptides have COOH‐terminal homoserine as expected from the presence of methionine at the carboxyl end of the native protein. One acetylated fragment was identified as the N‐terminal portion of the protein. The seven major fragments account for the amino‐acid composition of the entire protein; from the sum of their amino‐acid composition, a molecular weight of 37687 was calculated.