Role of the phosphotyrosine M2 motif in B-lymphocytes.

(A) TCLs from A20 cells expressing the indicated proteins were incubated with anti-Fyn antibodies and subjected to western blot analysis using the indicated antibodies. As control, aliquots of the same TCLs were analyzed with anti-Vav1 and anti-Myc antibodies to reveal the levels of endogenous Vav1 and ectopic M2 proteins present in these lysates. (B) M2-transfected A20 cells were lysed and TCLs analyzed either by immunoprecipitation with anti-M2 antibodies followed by immunoblot with the indicated antibodies (two upper panels) or by direct immunoblot with the indicated antibodies (rest of panels). The mobility of M2, Fyn and Vav1 proteins is indicated by arrowheads. The mobility of M2-dependent phosphorylated cellular proteins is indicated by arrows (fifth panel from top). α, anti; IP, immunoprecipitation; p, phosphorylated; WB, western blot.