Open reading frame yjbI of Bacillus subtilis codes for truncated hemoglobin

A hypothetical open reading frame from Bacillus subtilis genome, yjbI [NCBI genome database Accession No. ] having homology to many globin and globin-like proteins from different microbial genomes, was selectively amplified from the chromosomal DNA of B. subtilis strain DB104 based on genome sequence database of B. subtilis strain 168. The gene was cloned and over-expressed in Escherichia coli under the transcriptional control of tandem lambda P(L) and P(R) promoters, and the protein was purified to homogeneity. The single-chain monomeric hemoglobin-like protein is stable to the extent of 5.45 kcal/mol at 25 degrees C, binds carbon mono-oxide, and shows optical spectra characteristic of hemoproteins. The protein also exhibits peroxidase-like activity. This is the first report of a truncated bacterial globin endowed with peroxidase-like activity. The activity is enhanced in the presence of urea and guanidine hydrochloride, more so in the presence of the latter. Presumably, only a small portion of the protein is involved in peroxidase activity, which is exposed with increasing concentration of the denaturants.