SEQUENCE AND MOLECULAR CHARACTERIZATION OF A DNA REGION ENCODING A SMALL HEAT-SHOCK PROTEIN OF CLOSTRIDIUM-ACETOBUTYLICUM

A DNA region of Clostridium acetobutylicum containing a gene (hsp18) w ith significant homology to a family of small eukaryotic heat shock pr oteins was cloned and sequenced. It is the second reported sequence of a low-molecular-weight heat shock protein from gram-positive bacteria and is induced not only by heat shock but also at the onset of solven togenesis, as determined by Northern (RNA) blot analysis, thus confirm ing the results of an earlier study performed at the protein level (A. Pich, F. Narberhaus, and H. Bahl, Appl. Microbiol. Biotechnol. 33:697 -704, 1990). By primer extension analysis, a transcriptional start sit e was identified 149 bp upstream of hsp]8. This site was preceded by a region that exhibits high homology to the consensus promoter sequence s of gram-positive bacteria, as well as sigma70-dependent Escherichia coli. A direct repeat structure was detected in the -35 region. The pr omoter is located 196 bp from the start of a potential regulatory tRNA (ACG)Thr. gene involved in the shift to solventogenesis which is trans cribed in the opposite direction. A putative rho-independent transcrip tion termination structure was identified at the 3' end of hsp18.