Quantitation and significance of 125I-calmodulin binding to myosin light chain kinase and phosphorylase distributed on polyacrylamide gels.
Glycogen phosphorylase (a or b) binds 125I-calmodulin in a Ca2+-dependent manner, in the 125I-calmodulin overlay technique. This binding is quantitatively identical to 125I-calmodulin binding to myosin light chain kinase. In an in vitro assay, calmodulin stimulates phosphorylase activity at limiting concentrations of either glucose-1-phosphate or glycogen, but the Ka is 1000 fold higher than for the kinase, and is not Ca2+-dependent. Activation of phosphorylase, but not myosin light chain kinase, by calmodulin can be mimicked by troponin C or bovine serum albumin. These results demonstrate that the properties of calmodulin interaction with proteins can vary between the 125I-calmodulin technique and a functional assay of calmodulin effect on the same protein.
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism*; D004789:Enzyme Activation; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D008970:Molecular Weight; D009219:Myosin-Light-Chain Kinase; D010762:Phosphorylase a / Q000378:metabolism; D010763:Phosphorylase b / Q000378:metabolism; D006005:Phosphorylases / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D011817:Rabbits
D002147:Calmodulin; D010762:Phosphorylase a; D010763:Phosphorylase b; D006005:Phosphorylases; D011494:Protein Kinases; D009219:Myosin-Light-Chain Kinase; D002118:Calcium