Figure 3.

Sik-associated and GAP-associated 65-kDa proteins comigrate and are tyrosine-phosphorylated during differentiation. (A) Proteins from EMK cells incubated for 5 days in high Ca²⁺ medium were immunoprecipitated with anti-Sik antibodies with or without peptide block or with anti-GAP antibodies. Tyrosine-phosphorylated proteins were detected by using anti-phosphotyrosine antibodies. Sik protein comigrates with the Ig background band. Molecular size markers (kDa) are indicated on the left. (B) Tyrosine-phosphorylated proteins precipitated with anti-Sik or anti-GAP antibodies at different times after Ca²⁺ addition were detected with anti-phosphotyrosine antibodies.