Molecular cloning, sequence analysis and expression of the gene for catalase‐peroxidase (cpeA) from the photosynthetic bacterium Rhodobacter capsulatus B10

Abstract

The gene encoding catalase‐peroxidase was cloned from chromosomal DNA of Rhodobacter capsulatus B10. The nucleotide sequence of a 3.7‐kb SacI–HindIII fragment, containing the catalase‐peroxidase gene (cpeA) and its flanking regions were determined. A 1728‐bp open reading frame, coding for 576 amino acid residues (molecular mass 61516 Da) of the enzyme, was observed. A Shine‐Dalgarno sequence was found 5 bp upstream from the translational start site. The deduced amino acid sequence coincides with that of the amino terminus and of four peptides derived from trypsin digestion of the purified catalase‐peroxidase of R. capsulatus B10. The amino acid sequence of R. capsulatus catalase‐peroxidase shows interesting similarities to the amino acid sequences of the hydroperoxidases of Escherichia coli (42.7%) and Salmonella typhimurium (39.9%), the peroxidase of Bacillus stearothermophilus (32.1%) and the catalase‐peroxidase of Mycobacterium intracellulare (42.2%). As shown by a cpeA::lacZ fusion in trans in R. capsulatus, the expression of the catalase‐peroxidase gene is regulated by oxygen. The promoter of the cpeA gene was localized within 320 bp upstream of the ATG start codon.