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 f ragment, containing the catalase-peroxidase gene and its flanking regions w as determined. A 2.16 kb open reading frame was obtained, encoding the enzy me which was comprised of 720 amino acid residues with a calculated molecul ar weight of 80 kDa. The deduced amino acid sequence of the H. salinarum ca talase-peroxidase showed a high degree of identity to other bifunctional ca talase-peroxidases. A transcriptional start site was identified 183 bp upst ream of the translational start codon. Southern blot analysis indicated tha t catalase-peroxidase was a single copy gene. The Archaeal catalase-peroxid ase gene was expressed in Escherichia coli, and the expressed fusion protei n exhibited both catalase and peroxidase activities.