SEQUENCE AND TRANSCRIPTIONAL ANALYSIS OF CLPX, A CLASS-III HEAT-SHOCKGENE OF BACILLUS-SUBTILIS

The nucleotide sequence of clpX, which is localized between the tig (t rigger factor) and the ion (ATP-dependent protease) genes at 245 degre es on the standard Bacillus subtilis (Bs) genetic map, was determined. The putative clpX gene codes for a 46-kDa protein of 421 amino acid ( aa) residues. A comparison of the deduced aa sequence with those of th e recently described bacterial clpX gene products from Synechocystis s p., Escherichia coli (Ec), Haemophilus influenzae and Azotobacter vine landii revealed strong similarities. However, in contrast to Ec, clpX and clpP of Bs are located at different loci on the chromosome and are transcribed as monocistronic genes. A heat-inducible sigma(A)-like pr omoter was mapped upstream of the clpX structural gene, but no CIRCE e lement, characteristic of class-I heat-shock genes (e.g., groESL and d naK), was found between the transcriptional and translational start si tes. Although the majority of the heat-inducible general stress genes in Bs are under the control of the alternative sigma factor, sigma(B), the heat induction of clpX appears to be sigma(B)-independent. The la tter indicates that clpX belongs to class-III heat-inducible genes.