Calmodulin-binding proteins and calmodulin-regulated enzymes in dog pancreas.
Calmodulin was isolated and purified to homogeneity from dog pancreas. Highly purified subcellular fractions were prepared from dog pancreas by zonal sucrose-density ultracentrifugation and assayed for their ability to bind 125I-calmodulin in vitro. Proteins contained in these fractions were also examined for binding of 125I-calmodulin after their separation by polyacrylamide-gel electrophoresis in SDS. Calmodulin-binding proteins were detected in all subcellular fractions except the zymogen granule and zymogen-granule membrane fractions. One calmodulin-binding protein (Mr 240,000), observed in a washed smooth-microsomal fraction, has properties similar to those of alpha-fodrin. The postribosomal-supernatant fraction contained three prominent calmodulin-binding proteins, with apparent Mr values of 62,000, 50,000 and 40,000. Calmodulin-binding proteins, prepared from a postmicrosomal-supernatant fraction by Ca2+-dependent affinity chromatography on immobilized calmodulin, exhibited calmodulin-dependent phosphodiesterase, protein phosphatase and protein kinase activities. In the presence of Ca2+ and calmodulin, phosphorylation of smooth-muscle myosin light chain and brain synapsin and autophosphorylation of a Mr-50,000 protein were observed. Analysis of the protein composition of the preparation by SDS/polyacrylamide-gel electrophoresis revealed a major protein of Mr 50,000 which bound 125I-calmodulin. This protein shares characteristics with the calmodulin-dependent multifunctional protein kinase (kinase II) recently observed to have a widespread distribution. The possible role of calmodulin-binding proteins and calmodulin-regulated enzymes in the regulation of exocrine pancreatic protein synthesis and secretion is discussed.
D000818:Animals; D002147:Calmodulin / Q000378:metabolism*; D002148:Calmodulin-Binding Proteins / Q000378:metabolism*; D002499:Centrifugation, Density Gradient; D004285:Dogs; D004591:Electrophoresis, Polyacrylamide Gel; D008854:Microscopy, Electron; D010179:Pancreas / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure; D011494:Protein Kinases / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism / Q000648:ultrastructure
D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D011494:Protein Kinases