CYP116B5: a new class VII catalytically self-sufficient cytochrome P450 from A cinetobacter radioresistens that enables growth on alkanes.

A gene coding for a class VII cytochrome P450 monooxygenase ( CYP116B5) was identified from A cinetobacter radioresistens S13 growing on media with medium ( C14, C16) and long ( C24, C36) chain alkanes as the sole energy source. Phylogenetic analysis of its N- and C-terminal domains suggests an evolutionary model involving a plasmid-mediated horizontal gene transfer from the donor R hodococcus jostii RHA1 to the receiving A . radioresistens S13. This event was followed by fusion and integration of the new gene in A . radioresistens chromosome. Heterologous expression of CYP116B5 in E scherichia coli BL21, together with the A . radioresistens Baeyer- Villiger monooxygenase, allowed the recombinant bacteria to grow on long- and medium-chain alkanes, showing that CYP116B5 is involved in the first step of terminal oxidation of medium-chain alkanes overlapping AlkB and in the first step of sub-terminal oxidation of long-chain alkanes. It was also demonstrated that CYP116B5 is a self-sufficient cytochrome P450 consisting of a heme domain (aa 1-392) involved in the oxidation step of n-alkanes degradation, and its reductase domain (aa 444-758) comprising the NADPH-, FMN- and [ 2Fe2S]-binding sites. To our knowledge, CYP116B5 is the first member of this class to have its natural substrate and function identified. [ABSTRACT FROM AUTHOR]