Cloning, nucleotide sequence and structural analysis of the Clostridium acetobutylicum dnaJ gene

The complete dnaJ gene of Clostridium acetobutylicum was isolated by chromosome walking using the previously cloned 5' end of the gene as a probe. Nucleotide sequencing of a positively reacting 2.2-kb HincII fragment, contained in the recombinant plasmid pKG4, revealed that the reading frame of the dnaJ gene of C. acetobutylicum consists of 1125 bp, encoding a protein of 374 amino acids with a calculated M(r) of 40376 and an isoelectric point of 9.54. The deduced amino acid sequence showed high similarity to the DnaJ proteins of other bacteria (e.g. Escherichia coli, Bacillus subtilis) as well as of an archaeon (Methanosarcina mazei) and to the corresponding proteins of eukaryotes (Saccharomyces cerevisiae, Homo sapiens). The areas of similarity included a conserved N-terminal domain of about 70 amino acids, a glycine-rich region of about 30 residues, and a central domain containing four repeats of a CXXCXGXG motif, whereas the C-terminal domain was less conserved. Northern (RNA) blot analysis indicated that dnaJ is induced by heat shock and that it is part of the dnaK operon of C. acetobutylicum. The 5' end (901 bp) of another gene (orfB), downstream of dnaJ and not heat-inducible, showed no significant similarity to other sequences available in EMBL and GenBank databases.