Genetic diversity and expression of carbon monoxide dehydrogenase from Aeropyrum pernix

Abstract

The aerobic hyperthermophilic archaeon Aeropyrum pernix expresses molybdopterin carbon monoxide dehydrogenase (Mo-CODH). A. pernix strains isolated from Tachibana Bay (TB1–8) were found to exhibit different levels of total Mo-CODH activity (low and high, respectively), and the Mo-CODHs isolated from these strains also exhibit high or low activity. Mo-CODH gene transcription was detected by real-time reverse transcription-PCR, but no relation was found between the expression level of mRNA and the activity level of Mo-CODH. The nucleotide sequences of A. pernix genes encoding the small, large, and medium subunits of Mo-CODH, respectively, and those of the putative promoter region were identified from all TB strains. Amino acid substitutions were found in the sequences of high- and low-activity strains, but no mutation was detected in the putative promoter regions. Homology modeling revealed that all amino acid substitutions were localized on the surface of the Mo-CODH proteins. Based on these findings, we conclude that in A. pernix, the activity level of Mo-CODH may be regulated by translation or post-translational modification rather than by genomic diversity or transcription.