Comparison of tyrosine phosphorylation of proteins by membrane fractions from mouse liver, Ehrlich ascites tumor and MH134 hepatoma.

When membrane fractions from mouse liver, Ehrlich ascites tumor and MH134 hepatoma were incubated with [gamma-32P]ATP at 0 degree C in the presence of MnCl2, ZnCl2 and NaVO3, proteins were phosphorylated on tyrosines to a larger extent in liver membranes than in tumor membranes. Separation of labelled proteins by SDS-gel electrophoresis showed phosphorylated alkali-resistant bands of 170, 140, 130, 80, 56, 53 and 46 kDa proteins in Ehrlich ascites tumor membranes; liver membranes exhibited more strongly phosphorylated bands of 170, 56, 53 and 46 kDa proteins. Epidermal growth factor stimulated the tyrosine phosphorylation of only a 170 kDa protein, which was more significant in liver membranes. Liver membranes exhibited slightly higher levels of tyrosine protein kinase activity compared to tumor membranes.