title: Unique gene organization of thioredoxin and thioredoxin reductase in Mycobacterium leprae.
abstract: The thioredoxin system comprising thioredoxin (Trx), thioredoxin reductase (TR) and NADPH operates via redox-active disulphides and provides electrons for a wide variety of different metabolic processes in prokaryotic and eukaryotic cells. Thioredoxin is also a general protein disulphide reductase involved in redox regulation. In bacteria, the Trx and TR proteins previously identified were encoded by separate genes (trxA and trxB). In this study, we report a novel genomic organization of TR and Trx in mycobacteria and show that at least three modes of organization of TR and Trx genes can exist within a single bacterial genus: (i) in the majority of mycobacterial strains the genes coding for TR and Trx are located on separate sites of the genome; (ii) interestingly, in all pathogenic Mycobacterium tuberculosis complex mycobacteria both genes are found on the same locus, overlapping in one nucleotide; (iii) in the pathogen Mycobacterium leprae, TR and Trx are encoded by a single gene. Sequence analysis of the M. leprae gene demonstrated that the N-terminal part of the protein corresponds to TR and the C-terminal part to Trx. A corresponding single protein product of approximately 49 kDa was detected in cell extracts of M. leprae. These findings demonstrate the very unusual phenomenon of a single gene coding for both the substrate (thioredoxin) and the enzyme (thioredoxin reductase), which seems to be unique to M. leprae.
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D017931:DNA Primers; D004269:DNA, Bacterial / Q000737:chemistry; D005798:Genes, Bacterial; D016680:Genome, Bacterial; D006706:Homeostasis; D008969:Molecular Sequence Data; D009161:Mycobacterium / Q000235:genetics*; D009166:Mycobacterium leprae / Q000235:genetics* / Q000378:metabolism; D010084:Oxidation-Reduction; D016133:Polymerase Chain Reaction; D015183:Restriction Mapping; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D013880:Thioredoxin-Disulfide Reductase / Q000235:genetics*; D013879:Thioredoxins / Q000235:genetics*
chemical_list: D017931:DNA Primers; D004269:DNA, Bacterial; D013879:Thioredoxins; D013880:Thioredoxin-Disulfide Reductase