src gene product from different strains of avain sarcoma virus: Kinetics and possible mechanism of heat inactivation of protein kinase activity from cells infected by transformation-defective, temperature-sensitive mutant and wild-type virus

摘要

Sera from certain rabbits bearing Schmidt-Ruppin strain Rous sarcoma virus (RSV)-induced tumors precipitated p60src from chicken cells transformed by the homologous virus as well as by other strains [Prague strain RSV, Bryan high-titer strain RSV, and Bratislava 77 strain of avain sarcoma virus (ASV)], the molecular weights (Mrs) ranging from 60,000 to 64,000. The p60src immunoprecipitated from cells transformed by each of these strains incorporated [γ-32P]ATP into the Mr 53,000 subunit of IgG, though with differing activities. No such protein kinase activity (ATP:protein phosphotransferase, EC 2.7.1.37) was observed when the following immunoprecipitates were used: from uninfected cells, from untransformed cells infected by Rous-associated virus, or from cells transformed by acute leukosis viruses, avian erythroblastosis virus, or myelocytoma virus 29. The kinase reaction had a pH optimum at pH 5.9 and an apparent Km for ATP of 4.9 ± 2 μM, and was dependent on Mg2+ (Kb = 46 ± 12 mM), for which Ca2+ was no substitute. The kinase was cyclic AMP independent.