Abstract

The catA gene encodes the major catalase in Streptomyces coelicolor, whose production increases upon H_2O_2 treatment. Besides the previously identified primary promoter (catAp1), a minor promoter (catAp2) was newly assigned by S1 nuclease mapping. The catAp2 transcript was observed transiently upon entry into the stationary phase in liquid culture and upon differentiation on solid plates, whereas the level of catAp1 transcription did not change significantly during this growth transition. The catAp1 promoter was transcribed by the major vegetative RNA polymerase holoenzyme containing [sigma]^HrdB , whereas the catAp2 was transcribed in vitro by the holoenzyme containing [sigma]^R that is activated under oxidative conditions. The cis-element regulating the H_2 O_2 -inducibility of catAp1 was identified within the 23 bp inverted repeat sequence located between -65 and -43 of the catAp1 promoter. We named this sequence HRE (H_2O_2 -responsive element). The distal half of the inverted repeat was more crucial for H_2 O_2 ?pendent induction of the catAp1 transcript than the proximal half. HRE most likely serves as a binding site for the H_2 O_2 -responsive repressor CatR.

• Keywords: catA; CatR; H2O2 ; dual regulation; H 2 O 2 -responsive elements; Streptomyces coelicolor