ClpE, a novel type of HSP100 ATPase, is part of the CtsR heat shock regulon of Bacillus subtilis

Clp ATPases, which include the ubiquitous HSP100 family, are classified acc ording to their structural features and sequence similarities. During the c ourse of the Bacillus subtilis genome sequencing project, we identified a g ene encoding a new member of the HSP100 family. We designated this protein ClpE, as it is the prototype of a novel subfamily among the Clp ATPases, an d have identified homologues in several bacteria, including Listeria monocy togenes, Enterococcus faecalis, Streptococcus pyogenes, Streptococcus pneum oniae, Lactobacillus sakei and Clostridium acetobutylicum. A unique feature of these Hsp100-type Clp ATPases is their amino-terminal zinc finger motif . Unlike the other class III genes of B. subtilis (clpC and clpP), clpE doe s not appear to be required for stress tolerance. Transcriptional analysis revealed two sigma(A)-type promoters, expression from which was shown to be inducible by heat shock and puromycin treatment. Investigation of the regu latory mechanism controlling clpE expression indicates that this gene is co ntrolled by CtsR and is thus a member of the class III heat shock genes of B. subtilis. CtsR negatively regulates clpE expression by binding to the pr omoter region, in which five CtsR binding sites were identified through DNa se I footprinting and sequence analysis.