Open AccessPhosphorylation of Calmodulin by Plasma‐Membrane‐Associated Protein Kinase(s)
Author(s) -
BengurÍA Alberto,
Soriano Montserrat,
Joyal John L.,
Sacks David B.,
Villalobo Antonio
Publication year - 1995
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1995.050_c.x
Subject(s) - calmodulin , protein kinase a , biochemistry , phosphorylation , immunoprecipitation , biology , microbiology and biotechnology , chemistry , enzyme , gene
Plasma‐membrane‐associated protein kinase(s) from normal rat liver phosphorylates exogenous bovine brain calmodulin in the absence of Ca 2+ 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.