A serine-threonine-type protein kinase activity in the parent strain and chloramphenicol-resistant mutants of Streptomyces avermitilis

摘要

Extracts from cells of Streptomyces avermitilis 964 (ATSS 31272) and its chloramphenicol-resistant (Cml-r) mutants with increased levels of avermectin production were shown to display endogenous protein kinase activities. Incubation of S. avermitilis 964 extracts (isolated under conditions of physiological ionic strength) with [#gamma#-~(32)p]ATP resulted in the incorporation of radiolabeled phosphate into nine or ten polypeptide chains with molecular weights of 10-137 kDa. Two additional phosphorylated polypeptides with molecular weights of 83 and 75 kDa were found in Cml-r mutants. The maximum levels of ~(32)P_i incorporation into proteins were found in extracts of 13-15-hour-old cultures (rapid growth phase, RG1); these levels decreased twofold or threefold in extracts of 20-22-hour-old cultures (transitory growth phase, T), and recovered by the 30-40th hour of cultivation (rapid growth phase, RG2). Heparin, polylysine, spermine, phosphatidylserine, cAMP, cGMP, or Ca~(2+) did not affect the range and extent of polypeptide phosphorylation in the extracts. The protein kinase (or protein kinases) studied was shown to catalyze the attachment of phosphoryl groups to serine residues in polypeptides with molecular weights of 31, 61,75, and 79 kDa or residues of serine and threonine in the 83-kDa polypeptide.