title: Calcium/calmodulin-dependent protein kinase II in squid synaptosomes.
abstract: The Ca2+/calmodulin (CaM)-dependent protein kinase II system in squid nervous tissue was investigated. The Ca2+/CaM-dependent protein kinase II was found to be very active in the synaptosome preparation from optic lobe, where it was associated with the high-speed particulate fraction. Incubation of the synaptosomal homogenate with calcium, calmodulin, magnesium, and ATP resulted in partial and reversible conversion of the Ca2+/CaM-dependent protein kinase II from its calcium-dependent form to a calcium-independent species. The magnitude of this conversion reaction could be increased by inclusion of the protein phosphatase inhibitor NaF or by substitution of adenosine 5'-O-(3-thiotriphosphate) for ATP. When [gamma-32P]ATP was used, proteins of 54 and 58 kilodaltons (kDa) as well as proteins greater than 100 kDa were rapidly 32P-labeled in a calcium-dependent manner. Major 125I-CaM binding proteins in the synaptosome membrane fraction were 38 and 54 kDa. The Ca2+/CaM-dependent protein kinase II was purified from the squid synaptosome and was shown to consist of 54- and 58-60-kDa subunits. The purified kinase, like Ca2+/CaM-dependent protein kinase II from rat brain, catalyzed autophosphorylation associated with formation of the calcium-independent form. These studies, characterizing the Ca2+/CaM-dependent protein kinase II in squid neural tissue, are supportive of the putative role of this kinase in regulating calcium-dependent synaptic functions.
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002147:Calmodulin / Q000494:pharmacology; D049832:Decapodiformes / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology; D008970:Molecular Weight; D009899:Optic Lobe, Nonmammalian / Q000201:enzymology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D011494:Protein Kinases / Q000302:isolation & purification / Q000378:metabolism*; D012969:Sodium Fluoride / Q000494:pharmacology; D013574:Synaptosomes / Q000201:enzymology*
chemical_list: D002147:Calmodulin; C022571:adenosine 5'-O-(3-thiotriphosphate); D000255:Adenosine Triphosphate; D012969:Sodium Fluoride; D011494:Protein Kinases; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D008274:Magnesium; D002118:Calcium