CPTK71, A CYTOSOLIC PROTEIN-TYROSINE KINASE PREVIOUSLY PURIFIED FROM BOVINE PLATELETS, IS IDENTICAL WITH P72(SYK)

In the previous study, we reported purification and characterization o f cytosolic protein-tyrosine kinase, CPTK71, from bovine platelets (Na kamura, S., Yanagi, S. and Yamamura, H. (1988) Eur. J. Biochem. 174, 4 71-477). In the present study, we have investigated the relationship b etween CPTK71 and p72(syk) which was purified from cytosolic fraction of porcine spleen and sequenced from porcine cDNA library. The elution patterns of CPTK71 activity in each purification step closely corresp onded with the pattern of immunoreactivity with p72(syk). Immunoprecip itation study revealed that specific antibodies against p72(syk) preci pitated the activity of both phosphorylating [Val(5)]angiotensin II an d autophosphorylation of highly purified CPTK71. In addition, the same result was obtained using another anti-p72(syk) antibody which recogn ized different amino acid sequence of 72(sky). From these results, we conclude that CPTK71 is identical or closely related to p72(syk). (C) 1994 Academic Press, Inc. .