Characterization of the in vivo sites of serine phosphorylation on Lck identifying serine 59 as a site of mitotic phosphorylation.

The lymphocyte-specific protein-tyrosine kinase Lck plays a critical role in T cell activation. In response to T cell antigen receptor binding Lck undergoes phosphorylation on serine residues that include serines 59 and 194. Serine 59 is phosphorylated by ERK mitogen-activated protein kinase.