Phosphorylation of a Dogfish Skeletal Muscle Protein Related to Parvalbumin

Abstract

A class of proteins was isolated from the skeletal muscle of the Pacific dogfish (Squalus sucklii) with properties extremely similar to those of the parvalbumins in that they display the same characteristic UV-spectrum, strong affinity for calcium and immunological cross-reactivity with antibodies prepared against dogfish parvalbumin. Though they are found in three polymeric states with MW of ca. 350,000, 75,000, and 25,000, they dissociate in sodium dodecylsulfate into subunits of MW ca. 12,000 identical in size to the parvalbumins. The three high molecular weight species are readily phosphorylated by a cyclic nucleotide-independent dogfish protein kinase, but not by phosphorylase kinase. One phosphate is introduced per subunit which can be released by a dogfish protein phosphatase different from phosphorylase phosphatase. By contrast, no phosphorylation of parvalbumins could be demonstrated under any circumstances. These data might suggest that the phosphate-acceptor protein represents a physiologically active form of the parvalbumins.