Cloning of the Gene Encoding DNA Binding Protein HU from Bacillus stearothermophilus and Its Expression in Escherichia coli

The gene (hbst) encoding the DNA binding protein HU from Bacillus stearothermophilus was cloned, with the Bacillus subtilis HU gene (hbsu) as a hybridization probe. The nucleotide sequence, which contains a ribosome binding site, a transcriptional termination signal, as well as the coding region, was analyzed by the dideoxy chain-termination method. The deduced amino acid sequence of an open reading frame was perfectly matched with that of B. stearothermophilus HU (BstHU) determined by the protein chemical methods [M. Kimura and K. S. Wilson, J. Biol. Chem., 258, 4007-4011 (1983)]. The gene, hbst, was overexposed using the expression vector pET-5a in Escherichia coli, and the recombinant HU protein (r-BstHU) was purified to be homogeneity by heparin-agarose column chromatography followed by ion-exchange column chromatography on S-Sepharose. The recombinant protein thus obtained had a circular dichroism spectrum identical to that of the authentic protein and bound to DNA to the same extent as the authentic protein.