title: Calmodulin-stimulated protein kinase activity from rat pancreas.
abstract: Previous work from our laboratory has demonstrated that neurohumoral stimulation of the exocrine pancreas is associated with the phosphorylation of the Mr 29,000 ribosomal protein S6. In a cell-free system using pancreatic postmicrosomal supernatant as the kinase donor, we found that the following co-factors stimulate the phosphorylation of the Mr 29,000 ribosomal protein: calcium with calmodulin, calcium with phosphatidyl serine, and cAMP. These findings suggest that the pancreas contains a calcium-calmodulin-dependent protein kinase (CaM-PK) that can phosphorylate the Mr 29,000 ribosomal protein. A CaM-PK activity was partially purified sequentially by ion exchange, gel filtration, and calmodulin-affinity chromatography. Phosphorylation of the Mr 29,000 ribosomal protein by the partially purified CaM-PK was dependent on the presence of both calcium and calmodulin and not on the other co-factors. The CaM-PK fraction contained a phosphoprotein of Mr 51,000 whose phosphorylation was also dependent on calcium and calmodulin. When 125I-calmodulin-binding proteins from the CaM-PK fraction were identified using electrophoretic transfers of SDS-polyacrylamide gels, a single Mr 51,000 protein was labeled. The preparation enriched in CaM-PK activity contained an Mr 51,000 protein that underwent phosphorylation in a calcium-calmodulin-dependent manner and an Mr 51,000 calmodulin-binding protein. It is therefore possible that the CaM-PK may comprise a calmodulin-binding phosphoprotein component of Mr 51,000.
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000032:analysis; D002147:Calmodulin / Q000494:pharmacology*; D008970:Molecular Weight; D010179:Pancreas / Q000032:analysis / Q000201:enzymology*; D010766:Phosphorylation; D011494:Protein Kinases / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D012269:Ribosomal Proteins / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; D002147:Calmodulin; D012269:Ribosomal Proteins; D011494:Protein Kinases; D002118:Calcium