The putative anti-anti-sigma factor BIdG is post-translationally modified by phosphorylation in Streptomyces coelicolor

The Streptomyces coelicolor bldG gene encodes a protein showing similarity to the SpollAA and RsbV anti-anti-sigma factors of Bacillus subtilis. Purified maltose binding protein-BldG could be phosphorylated in vitro by wild-type S. coelicolor crude extract, and both the phosphorylated and unphosphorylated forms of BldG could be detected in vivo using isoelectric focusing. ATP was shown to serve as the phosphoryl group donor, and phosphorylation of BldG was abolished when the putative phosphorylation site was changed from a serine to an alanine residue. A bldG mutant strain expressing the non-phosphorylatable BldG protein was unable to undergo morphological differentiation or produce antibiotics even after prolonged incubation, suggesting that phosphorylation of BldG is necessary for proper development in S. coelicolor. (C) 2003 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.