Characterization of calmodulin and calmodulin isotypes from sea urchin gametes

Abstract

Procedures were developed for the purification of calmodulin from the eggs and from the sperm of the sea urchin Strongylocentrotus purpuratus and Arbacia punctulata. Two forms of calmodulin were isolated from A. punctulata eggs, one from each of the other three sources. All five calmodulins are similar to vertebrate calmodulin as judged by their activation of bovine brain cyclic nucleotide phosphodiesterase, calcium-dependent interaction with troponin I and with chloropromazine, increased anode mobility on sodium dodecyl sulfate gels in the presence of calcium, cross-reactivity with anti-vertebrate calmodulin antibodies and amino acid compositions including the presence of a single residue of trymethyllysine. The two forms of calmodulin from A. punctulata eggs, calmodulin A and calmodulin B, can be distinguished from one another on the basis of DEAE-cellulose chromatography, amino acid analysis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the presence or absence of calcium and competitive radioimmunoassays. There is no evidence that either form is a proteolytic product of the other.