The clpP multigenic family in Streptomyces lividans: conditional expression of the clpP3 clpP4 operon is controlled by PopR, a novel transcriptional activator

The clpP genes are widespread among living organisms and encode the proteol ytic subunit of the Clp ATP-dependent protease. These genes are present in a single copy in most eubacteria. However, five clpP genes were identified in Streptomyces coelicolor. The clpP1 clpP2 operon was studied: mutations a ffected the growth cycle in various Streptomyces. Here, we report studies o f the expression of the clpP3 clpP4 operon in Streptomyces lividans. The cl pP3 operon was induced in a clpP1 mutant strain, and the regulation of expr ession was investigated in detail. The product of the putative regulator ge ne, downstream from clpP4, was purified. Gel migration shift assays and DNa se I footprinting showed that this protein binds to the clpP3 promoter and recognizes a tandem 6 bp palindromic repeat (TCTGCC-3N-GGCAGA). In vivo, th is DNA-binding protein, named PopR, acts as an activator of the clpP3 opero n. Studies of popR expression indicate that the regulator is probably contr olled at the post-transcriptional level.