Expression and characterization of Streptomyces coelicolor serine/threonine protein kinase PkaE.

We identified and characterized a new eukaryotic-type protein kinase (PkaE) from Streptomyces coelicolor A3 (2) M145. PkaE, consisting of 510 amino acid residues, is a cytoplasmic protein kinase and contains the catalytic domain of eukaryotic protein kinases in the N-terminal region. Recombinant PkaE was found to be autophosphorylated at threonine residues only. The disruption of chromosomal pkaE resulted in the overproduction of the actinorhodin-related blue pigment antibiotics. pkaE was expressed during the late growth phase in S. coelicolor A3 (2) M145, which corresponded to the production time of blue pigments. This result indicated that PkaE acts as a negative regulator for production of the secondary metabolites. In addition, PkaE was able to phosphorylate KbpA, a regulator involved in the AfsK-AfsR regulatory pathway.