title: Involvement of protein kinase C in the phosphorylation of an insulin-granule membrane protein.
abstract: The involvement of protein kinase C in the Ca2+-dependent phosphorylation of a 29 000-Mr insulin-granule membrane protein prepared from a rat insulinoma was investigated. Protein kinase C activity towards exogenous lysine-rich histone was detected in a cytosolic fraction prepared from an insulinoma homogenate in the presence of EGTA. This activity bound reversibly to insulin granules in a Ca2+-dependent manner. Phosphatidylserine liposomes removed both protein kinase C activity and the 29 000-Mr protein-phosphorylating activity from the cytosolic fraction in a Ca2+-dependent fashion. Protein kinase C activity and the enzymic activity responsible for the phosphorylation of the 29 000-Mr granule protein behaved identically on sucrose-density-gradient centrifugation, ion-exchange chromatography, (NH4)2SO4 fractionation and gel filtration of the cytosolic fraction. These results are consistent with protein kinase C being the enzyme responsible for the phosphorylation of the 29 000-Mr insulin-granule membrane protein.
mesh_terms: D007516:Adenoma, Islet Cell / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002499:Centrifugation, Density Gradient; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003594:Cytoplasmic Granules / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D066298:In Vitro Techniques; D007328:Insulin; D007340:Insulinoma / Q000201:enzymology / Q000378:metabolism*; D008081:Liposomes / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000378:metabolism*; D010190:Pancreatic Neoplasms / Q000201:enzymology / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats
chemical_list: D007328:Insulin; D008081:Liposomes; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D011494:Protein Kinases; D011493:Protein Kinase C; D002118:Calcium