Molecular cloning, sequencing analysis and expression of the catalase-peroxidase gene from Halobacterium salinarum

The gene encoding catalase-peroxidase was cloned from chromosomal DNA from the Archaea, Halobacterium salinarum. The nucleotide sequence of a 3.5 kb fragment, containing the catalase-peroxidase gene and its flanking regions was determined. A 2.16 kb open reading frame was obtained, encoding the enzyme which was comprised of 720 amino acid residues with a calculated molecular weight of 80 kDa. The deduced amino acid sequence of the H. salinarum catalase-peroxidase showed a high degree of identity to other bifunctional catalase-peroxidases. A transcriptional start site was identified 183 bp upstream of the translational start codon. Southern blot analysis indicated that catalase-peroxidase was a single copy gene. The Archaeal catalase-peroxidase gene was expressed in Escherichia coli, and the expressed fusion protein exhibited both catalase and peroxidase activities.