Bacterial cytochromes P450-Studies on Cytochrome P450 102A2 and P450 102A3 of Bacillus subtilis

Cytochromes P450 constitute a super-family of heme containing mixed function mono-oxygenases that is found in all branches of life. They introduce single oxygen atoms, mostly in the form of hydroxyl groups, into lipophilic substances and thereby render them more hydrophilic and susceptible to further reactions. Little is known about the bacterial cytochromes P450. I have in my thesis given an overview of the bacterial cytochromes P450 with emphasis on the Bacillus subtilis P450s that have been the subject of my Ph.D. studies. B. subtilis is the most well-studied bacterium next to Escherichia coli and is a model-organism for the Gram-positive bacteria. There are eight cytochromes P450 in B. subtilis strain 168 of which three have been the subject of my research. The function of cytochrome P450 107J1 (Cyp107J1) is not known. Cyp102A2 and Cyp102A3 are fatty acid hydroxylases that show preferences for long-chain unsaturated and branched-chain fatty acids. The gene for Cyp102A3 is preceded by and lies in an operon with the gene for a fatty acid displaced transcriptional repressor, FatR. FatR binds and is displaced from its operator by unsaturated and branched-chain fatty acids, thereby allowing transcription. The cyp102A2 and fatR-cyp102A3 operons are expressed in the stationary phase and are controlled by the global transcriptional regulators Spo0A and AbrB, involving a novel B. subtilis pheromone. When studying Cyp107J1 a novel mode of resistance against the toxic leucine analogue, 4-azaleucine, was found. The resistance phenotype is due to a loss of function mutation in a transcriptional repressor, with the concomitant over-production of two membrane proteins.