Dynamics of serine/threonine protein kinase activity during the growth of the wild-type Streptomyces avermitilis strain and its chloramphenicol-resistant mutant

The dynamics of serine/threonine protein kinase activity during the growth of the wild-type Streptomyces avermitilis strain 964 and its chloramphenico l-resistant (Cml(r)) pleiotropic mutant with an enhanced production of aver mectins was studied by measuring the transfer of radiolabeled phosphate fro m [gamma-P-32]ATP to the serine and threonine residues of proteins in cell- free extracts. In both of the strains studied, radiolabeled phosphate was f ound to incorporate into polypeptides with molecular masses of 32, 35, 41, 68, 75, 79, 83, and 137 kDa; however, the degree and the dynamics of phosph orylation of particular peptides were different in these strains. The diffe rences revealed could not be accounted for by the interference of ATPases o r phosphoprotein phosphatases. The data obtained may be interpreted as evid ence that Cml(r) mutation activates the protein kinase signalling system of S. avermitilis cells in the early stationary growth phase and thus enhance s the production of avermectins and leads to some other physiological chang es in the mutant strain.