A developmentally regulated catalase required for proper differentiation and osmoprotection of Streptomyces coelicolor

Streptomyces coelicolor produces at least three catalases, the expression o f which varies under different conditions. We characterized a gene (catB) f or developmentally controlled catalase of 779 amino acids (83408 Da), homol ogous to KatE of Escherichia coil and Bacillus subtilis. Expression of the catB gene increased at the stationary phase in liquid culture and after the onset of differentiation on solid culture. It was also increased by osmoti c treatments. Transcription was initiated from a promoter (catBp), whose se quence (ATGCCTCG-N-13-GGGTAC) resembled promoters recognized by sigma(B) of B. subtilis. Cats protein underwent proteolytic cleavage of its N-terminal 95 amino acids and was secreted to the medium when cells sporulated. Disru ption of the catB gene caused impairment in the formation of aerial myceliu m and reduction in the synthesis of undecylprodigiosin. On the contrary, hy perproduction of actinorhodin was observed in accordance with the increase in actII-ORF4 transcription. In addition, catB mutant became hypersensitive to osmotic stresses. These results suggest that regulated synthesis of Cat s protein is necessary to ensure proper differentiation as well as to prote ct S. coelicolor cells against osmotic stresses.