Calmodulin from the water mold Achlya ambisexualis: isolation and characterization

A protein-activator of bovine cyclic nucleotide phosphodiesterase from the water mold Achlya ambisexualis has been affinity-purified to apparent electrophoretic homogeneity. The heat-stable protein is similar in amino acid content and electrophoretic mobility on SDS acrylamide gels, to bovine brain calmodulin. It also cross-reacts with antibodies raised to the bovine protein. Achlya calmodulin activates PDE increasing its activity up to 9-fold in a Ca2+-dependent manner. The mold protein appears unusual in that its tyrosine fluorescence is unaltered by Ca2+ or by EGTA.