Benguría A, Hernández-Perera O, Martínez-Pastor M T, Sacks D B, Villalobo A
Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
Eur J Biochem. 1994 Sep 15;224(3):909-16. doi: 10.1111/j.1432-1033.1994.00909.x.
An epidermal-growth-factor(EGF)-receptor preparation isolated by calmodulin-affinity chromatography from rat liver plasma membranes is able to phosphorylate calmodulin. Calmodulin phosphorylation was enhanced 3-8-fold by EGF, was dependent on the presence of a polycation or basic protein and was inhibited by micromolar concentrations of Ca2+. Phosphate incorporation into calmodulin occurs predominantly on tyrosine residues. Partial proteolysis of phosphocalmodulin by thrombin identifies Tyr99, located in the third calcium-binding domain of calmodulin, as the phosphorylated residue. Stoichiometric measurements show a 32P/calmodulin molar ratio of approximately 1 when optimal phosphorylation conditions are used.
