Involved in negative regulation of cell growth. Has tumor suppressor properties. Plays a negative regulatory role in the Ras-MAPK pathway. May function in signaling pathways utilized broadly during fetal development and more selectively in adult tissues and in cells of the lymphohematopoietic system. Could specifically be involved in phospholipid signal transduction. ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Interacts with the SH3 domain of PLCG1 via its Pro-rich domain. Expressed in all umbilical cord blood, bone marrow and adult blood cell sub-populations and in several leukemia cell lines. Highly expressed in fetal blood, brain, lung, liver and kidney. Detected at lower levels in adult prostate, testis, ovary, small intestine and colon. Not expressed in adult lung, liver, kidney or brain. Autophosphorylated on tyrosine residues. Belongs to the protein kinase superfamily. Tyr protein kinase family.