The role of C2 domains in Ca2+-activated and Ca2+-independent protein kinase Cs in aplysia.
In the nervous system of the marine mollusk Aplysia there are two protein kinase C (PKC) isoforms, the Ca2+-activated PKC Apl I and the Ca2+-independent PKC Apl II. PKC Apl I, but not PKC Apl II is activated by a short-term application of the neurotransmitter serotonin. This may be explained by the fact that purified PKC Apl II requires a higher mole percentage of phosphatidylserine to stimulate enzyme activity than does PKC Apl I. In order to understand the molecular basis for this difference, we have compared the ability of lipids to interact with the purified kinases and with regulatory domain fusion proteins derived from the kinases using a variety of assays including kinase activity, phorbol dibutyrate binding, and liposome binding. We found that a C2 domain fusion protein derived from PKC Apl I binds to lipids constitutively, while a C2 domain fusion protein derived from PKC Apl II does not. In contrast, fusion proteins containing the C1 domains of PKC Apl I and PKC Apl II showed only small differences in lipid interactions. Thus, while the presence of a C2 domain assists lipid-mediated activation of PKC Apl I, it inhibits activation of PKC Apl II.
Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec H3A 2B4, Canada.
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Pepio
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Fan
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Sossin
D000818:Animals; D001048:Aplysia / Q000201:enzymology*; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D004789:Enzyme Activation; D007527:Isoenzymes / Q000378:metabolism*; D050356:Lipid Metabolism; D015240:Phorbol 12,13-Dibutyrate / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism
D007527:Isoenzymes; D011993:Recombinant Fusion Proteins; D012701:Serotonin; D015240:Phorbol 12,13-Dibutyrate; D011493:Protein Kinase C; D002118:Calcium