Phosphorylation of calmodulin by plasma-membrane-associated protein kinase(s).
Plasma-membrane-associated protein kinase(s) from normal rat liver phosphorylates exogenous bovine brain calmodulin in the absence of Ca2+ and in the presence of histone or poly(L-lysine). Maximum levels of calmodulin phosphorylation are obtained at a poly(L-lysine)/calmodulin molar ratio of 0.4. Phosphoamino acid analysis revealed that calmodulin is phosphorylated on serine, threonine and tyrosine residues. Endogenous plasma-membrane-associated calmodulin was also phosphorylated by plasma-membrane-associated protein kinase(s) in the absence of added cationic protein or polypeptide. The identity of endogenous phosphocalmodulin was confirmed by immunoprecipitation with a specific anti-calmodulin monoclonal antibody. Ehrlich ascites tumor cell plasma membranes do not contain endogenous calmodulin. However, membrane-associated protein kinase(s) from these tumor cells phosphorylates bovine brain calmodulin in the presence of poly(L-lysine). These data demonstrate that phosphocalmodulin is present in liver plasma membranes and suggest that this post-translational modification could have a physiological role in this location.
Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
A
A
Benguría
M
M
Soriano
J L
JL
Joyal
D B
DB
Sacks
A
A
Villalobo
D000818:Animals; D001921:Brain / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism*; D002412:Cations; D002417:Cattle; D002462:Cell Membrane / Q000201:enzymology; D008099:Liver / Q000201:enzymology*; D008297:Male; D051379:Mice; D010455:Peptides / Q000378:metabolism; D010766:Phosphorylation; D011233:Precipitin Tests; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014407:Tumor Cells, Cultured
D002147:Calmodulin; D002412:Cations; D010455:Peptides; D011494:Protein Kinases