Developmental regulation of tyrosine phosphorylation substrates calpactin 1 and vinculin in embryonic avian limb and expression in cultured limb cells

Phosphotyrosine-containing proteins are minor components of normal cells that, in certain instances, are associated with the regulation of cellular metabolism and growth. An increase in the phosphotyrosine content of cellular proteins is observed following transformation by several avian sarcoma viruses. Two of the most prominent cellular substrates are calpactin 1 and vinculin. Both proteins are phosphorylated at tyrosine following transformation by retroviruses. To determine the sites of calpactin and vinculin synthesis frozen sections were prepared and stained with anti-calpactin and anti-vinculin serum