Y¹²⁰ is the predominant tyrosine required for the formation of the M2/Vav1/Fyn complex and for M2-dependent phosphorylation of Vav1.

<p>COS1 cells were transiently transfected with plasmids encoding the indicated proteins. (A,B) Cells were lysed and clarified extracts incubated with either anti-M2 (A) or anti-Vav1 antibodies (B). Immunoprecipitates were analysed by western blot with the indicated antibodies (right side of panels). Western blot analysis of a representative aliquot of total cell lysates (TCL) confirmed expression of proteins (bottom panels). (C) Cell lysates were incubated with an anti-Vav1 antibody and the resulting immunoprecipitates subjected to an immunocomplex kinase assay exactly as described previously <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0001654#pone.0001654-Rodrigues1" target="_blank">[22]</a>. Lower panel is an overexposure showing phosphorylation of M2 and its mutant forms. The position of molecular weight markers is indicated on the right. −, without; +, with; α, anti; IP, immunoprecipitation; p, phosphorylated; WB, western blot.