Alteration of serine/threonine protein kinase activity during 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 and its chloramphenicol-resistant (Cmlr) pleiotropic mutant with an enhanced production of avermectins was studied by measuring the transfer of radiolabeled phosphate from gamma-32P]ATP to the serine and threonine residues of proteins in cell-free extracts. In both of the strains studied, radiolabeled phosphate was found 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 phosphorylation of particular peptides were different in these strains. The differences revealed could not be accounted for by the interference of ATPases or phosphoprotein phosphatases. The data obtained may be interpreted as evidence that Cmlr mutation activates the protein kinase signalling system of S. avermitilis cells in the early stationary growth phase and thus enhances the production of avermectins and leads to some other physiological changes in the mutant strain.