Identification of the Regulator Gene Responsible for the Acetone-Responsive Expression of the Binuclear Iron Monooxygenase Gene Cluster in Mycobacteria

• Published in: Journal of Bacteriology Vol. 193; no. 20; pp. 5817 - 5823
• Main Authors: Furuya, Toshiki, Hirose, Satomi, Semba, Hisashi, Kino, Kuniki
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for Microbiology 01-10-2011
• Subjects: acetoin; acetone; Acetone - metabolism; Amino Acid Sequence; amino acids; Bacteria; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacteriology; Base Sequence; Biological and medical sciences; Enzymes; Fundamental and applied biological sciences. Psychology; Gene expression; Gene Expression Regulation, Bacterial; Gene Expression Regulation, Enzymologic; Genes, Regulator; Genetics and Molecular Biology; Genomes; green fluorescent protein; intergenic DNA; Iron - metabolism; metabolism; Microbiology; Miscellaneous; Mixed Function Oxygenases - genetics; Mixed Function Oxygenases - metabolism; Molecular Sequence Data; Multigene Family; Mycobacterium - chemistry; Mycobacterium - enzymology; Mycobacterium - genetics; Mycobacterium - metabolism; Mycobacterium goodii; Mycobacterium smegmatis; Mycobacterium smegmatis - chemistry; Mycobacterium smegmatis - enzymology; Mycobacterium smegmatis - genetics; Mycobacterium smegmatis - metabolism; nucleotide sequences; phenol; Plasmids; propane; regulator genes; Sequence Alignment; sequence analysis; transcription (genetics); transcription factors; Gene cluster; Mycobacterium; Mycobacteriales; Mycobacteriaceae; Regulator gene; Bacteria; Actinomycetes; Iron; Identification
• ISSN: 0021-9193; 1098-5530; 1067-8832
• DOI: 10.1128/JB.05525-11

The mimABCD gene cluster encodes the binuclear iron monooxygenase that oxidizes propane and phenol in Mycobacterium smegmatis strain MC2 155 and Mycobacterium goodii strain 12523. Interestingly, expression of the mimABCD gene cluster is induced by acetone. In this study, we investigated the regulator gene responsible for this acetone-responsive expression. In the genome sequence of M. smegmatis strain MC2 155, the mimABCD gene cluster is preceded by a gene designated mimR, which is divergently transcribed. Sequence analysis revealed that MimR exhibits amino acid similarity with the NtrC family of transcriptional activators, including AcxR and AcoR, which are involved in acetone and acetoin metabolism, respectively. Unexpectedly, many homologs of the mimR gene were also found in the sequenced genomes of actinomycetes. A plasmid carrying a transcriptional fusion of the intergenic region between the mimR and mimA genes with a promoterless green fluorescent protein (GFP) gene was constructed and introduced into M. smegmatis strain MC2 155. Using a GFP reporter system, we confirmed by deletion and complementation analyses that the mimR gene product is the positive regulator of the mimABCD gene cluster expression that is responsive to acetone. M. goodii strain 12523 also utilized the same regulatory system as M. smegmatis strain MC2 155. Although transcriptional activators of the NtrC family generally control transcription using the σ54 factor, a gene encoding the σ54 factor was absent from the genome sequence of M. smegmatis strain MC2 155. These results suggest the presence of a novel regulatory system in actinomycetes, including mycobacteria.