Could play a significant role in the signal transduction of hematopoietic cells. May regulate tyrosine kinase activity of SRC-family members in brain. ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Interacts with KIT. In platelets, 90% of MATK localizes to the membrane fraction, and translocates to the cytoskeleton upon thrombin stimulation. Enriched in lymphoid tissues. Belongs to the protein kinase superfamily. Tyr protein kinase family. CSK subfamily.