Tyrosine-protein kinase Lyn, also known as LYN, is a member of the src family of non-receptor protein tyrosine kinases that is predominantly expressed in haematopoietic tissues. This protein is Involved in induction of stress-activated protein kinase (SAPK), but not ERK or p38 MAPK, in response to genotoxic agents. It Induces SAPK by a MKK7- and MEKK1-dependent mechanism. The LYN -> MEKK1 -> MKK7 -> SAPK pathway is functional in the induction of apoptosis by genotoxic agents. Recombinant human LYN protein, fused to His-tag at N-terminus, was expressed in E.coli.