By using an internal part of the dnaK gene from BaciUlus megaterium as a probe, a 5.2-kb Hindlll fragment of chromosomal DNA of BaciUlus subtilis was cloned. Downstream sequences were isolated by in vivo chromosome walking. Sequencing of 5,085 bp revealed four open reading frames in the order orf9-grpEdnaK-dnaJ. orJ39 encodes a 39-kDa polypeptide of unknown biological function with no noticeable homology to any other protein within the data bases. Alignment of the GrpE protein with those of three other bacterial species revealed a low overall homology, but a higher homology restricted to two regions which might be involved in interactions with other proteins. Alignment of the DnaK protein with six bacterial DnaK polypeptides revealed that a contiguous region of 24 amino acids is absent from the DnaK proteins of all known gram-positive species. Primer extension studies revealed three potential transcription start sites, two preceding orJ39 (Si and S2) and a third one in front of grpE (S3). S2 and S3 were activated at a high temperature. Northern (RNA) analysis led to the detection of three mRNA species of 4.9, 2.6, and 1.5 kb. RNA dot blot experiments revealed an at-least-fivefold increase in the amount of specific mRNA from 0 to 5 min postinduction and then a rapid decrease. A transcriptional fusion between dnaK and the amyL reporter gene exhibited a slight increase in a-amylase activity after heat induction. A 9-bp inverted repeat was detected in front of the coding region of orJ39. This inverted repeat is present in a number of other heat shock operons in other microorganisms ranging from cyanobacteria to mycobacteria. The biological property of this inverted repeat as a putative key element in the induction of heat shock genes is discussed. The dnaK locus was mapped at about 2230 on the B. subtilis genetic map.The heat shock response is a homeostatic mechanism that enables cells to survive a variety of environmental stresses. It is characterized by the increased synthesis of a group of evolutionarily conserved proteins, heat shock proteins (HSPs), and is a universal feature of both prokaryotic and eukaryotic cells (35). When Eschertichia coli cells are shifted to a high temperature, the synthesis of a set of about 20 HSPs transiently increases and then declines rapidly to steady-state levels characteristic of the new ambient temperature (44).The highly conserved HSPs perform similar functions in all organisms. One of these functions is the well-established regulation of protein-protein interactions by the chaperonins (69). One of the most abundant HSPs, HSP70, is highly conserved in evolution. It is found in such diverse organisms as E. coli, Saccharomyces cerevisiae, Drosophila melanogaster, and Homo sapiens (14, 35).The dnaK gene of E. coli was originally discovered because mutations in it blocked bacteriophage lambda DNA replication at all temperatures (22,23). Subsequently, the dnaK gene product was shown to be essential for E. coli viability at high and low temperatures (22,30,46,51,52), and genetic evid...

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To find out whether Escherichia coli heat shock promoters are recognized in Bacillus subtilis, the regulatory regions including the heat shock promoters of the main heat shock genes dnaKJ, lon, groES, and htpG were fused to the indicator genes lacZ and cat. Whereas all transcriptional fusions were expressed in E. coli at low temperature and transient increases of β‐galactosidase activity could be measured at the inducting temperature, no enzymatic activity was found in B. subtilis. This indicates that E. coli heat shock promoters are nonfunctional in B. subtilis.