title: Heat-stable calmodulin-binding protein in rat testis. Inhibition of calmodulin-stimulated cyclic nucleotide phosphodiesterase activity.
abstract: An inhibitor of procine brain calmodulin-dependent cyclic nucleotide phosphodiesterase was purified about 940-fold from rat testis. This inhibitor inhibited the calmodulin-induced activation of the enzyme without affecting its basal activity. The inhibitor activity was counteracted by a high concentration of calmodulin, but was not by a high concentration of Ca2+. The analysis on polyacrylamide disc gel electrophoresis demonstrated that the inhibitor and calmodulin form a complex in the presence of Ca2+ but not in the presence of excess amount of EGTA. This inhibitor also inhibited the calmodulin-induced activation of Ca2+, Mg2+ -ATPase of human erythrocytes. The inhibitor appeared to be a heat-stable protein, since the inhibitor activity was not attenuated by boiling up to 9 min but was completely abolished by tryptic or chymotryptic digestion. The molecular weights of the inhibitor determined by linear polyacrylamide gradient gel electrophoresis under nondenaturing conditions and sodium dodecyl sulfate-polyacrylamide gel electrophoresis were 40,000 and 32,000, respectively. Thus, the inhibitor is suggested to be a calmodulin-binding protein composed of a monomer which has unique properties different from those of other tissues.
mesh_terms: D015087:2',3'-Cyclic-Nucleotide Phosphodiesterases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology; D002147:Calmodulin / Q000378:metabolism*; D002148:Calmodulin-Binding Proteins; D004533:Egtazic Acid / Q000494:pharmacology; D010450:Endopeptidases; D007700:Kinetics; D008297:Male; D008970:Molecular Weight; D010726:Phosphodiesterase Inhibitors; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors* / Q000302:isolation & purification / Q000378:metabolism; D010727:Phosphoric Diester Hydrolases; D011487:Protein Conformation; D051381:Rats; D011919:Rats, Inbred Strains; D013737:Testis / Q000201:enzymology*
chemical_list: D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D010726:Phosphodiesterase Inhibitors; C051666:calspermin; D004533:Egtazic Acid; D010749:Phosphoprotein Phosphatases; D015087:2',3'-Cyclic-Nucleotide Phosphodiesterases; D010727:Phosphoric Diester Hydrolases; D010450:Endopeptidases; D002118:Calcium