The AbrB protein of B. subtilis represses the transcription of various postexponentially expressed genes, such as the antibiotic biosynthesis gene tycA. Recently, we have shown that AbrB binds to the tycA promoter region at two A+T-rich sites; the ‘promoter site’ (−60 to −35) and the ‘leader site’ (+169 to +231). In this study we demonstrate that a P tyc —lacZ fusion missing the leader region is constitutively expressed in wild-type B. subtilis cells and in B. subtilis cells carrying spoOA or abrB mutations. We also show that substitution mutations within the recently reported potential helix-turn-helix DNA binding motif of AbrB did not affect its specific DNA binding ability.
