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Calcium/Calmodulin‐Dependent Protein Kinase II in Squid Synaptosomes
Author(s) -
Bass Martha,
Pant Harish C.,
Gainer Harold,
Soderling Thomas R.
Publication year - 1987
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1987.tb10001.x
Subject(s) - synaptosome , protein kinase a , calmodulin , calcium , biochemistry , biology , kinase , protein kinase c , cgmp dependent protein kinase , calcium binding protein , chemistry , mitogen activated protein kinase kinase , enzyme , in vitro , organic chemistry
Abstract: The Ca 2+ /calmodulin (CaM)‐dependent protein kinase II system in squid nervous tissue was investigated. The Ca 2+ /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 Ca 2+ /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 [γ‐ 32 P] ATP was used, proteins of 54 and 58 kilodaltons (kDa) as well as proteins >100 kDa were rapidly 32 P‐labeled in a calcium‐dependent manner. Major 125 I‐CaM binding proteins in the synaptosome membrane fraction were 38 and 54 kDa. The Ca 2+ /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 Ca 2+ /CaM‐dependent protein kinase II from rat brain, catalyzed auto‐phosphorylation associated with formation of the calcium‐independent form. These studies, characterizing the Ca 2+ / CaM‐dependent protein kinase II in squid neural tissue, are supportive of the putative role of this kinase in regulating calcium‐dependent synaptic functions.