title: Characterization of a manganese-dependent regulatory protein, TroR, from Treponema pallidum.
abstract: Genome sequence analysis of Treponema pallidum, the causative agent of syphilis, suggests that this bacterium has a limited iron requirement with few, if any, proteins that require iron. Instead, T. pallidum may use manganese-dependent enzymes for metabolic pathways. This strategy apparently alleviates the necessity of T. pallidum to acquire iron from the host, thus overcoming iron limitation, which is a primary host defense. Interestingly, a putative metal-dependent regulatory protein, TroR, which has homology with the diphtheria toxin regulatory protein, DtxR, from Corynebacterium diphtheriae was identified from T. pallidum. We describe here the characterization of TroR, a regulatory protein. Mobility-shift DNA binding and DNase I footprint assays indicated that purified TroR bound to a 22-nt region of dyad symmetry that overlaps the -10 region of the promoter of the tro operon, which contains the genes for a putative metal transport system, the glycolytic enzyme phosphoglycerate mutase, and TroR. Unlike other metal-dependent regulatory proteins like diphtheria toxin regulatory protein and the ferric ion uptake regulator, Fur, which can be activated by divalent metals such as Fe(2+), Mn(2+), Co(2+), Ni(2+), and Zn(2+), TroR is activated only by Mn(2+). The TroR-Mn(2+) complex binds its target sequence and blocks transcription of the troPO/lacZ fusion, suggesting that TroR acts as a metal-dependent repressor in vivo. In addition, TroR exists as a dimer in both its inactive (metal free) and active states as indicated by chemical crosslinking experiments. Based on these data, we propose that TroR represents a unique regulatory system for controlling gene expression in T. pallidum in response to Mn(2+).
authors.affiliation: The Department of Microbiology, The University of Georgia, Athens, GA 30602, USA.
authors.forename: J E
authors.initials: JE
authors.lastname: Posey
authors.forename: J M
authors.initials: JM
authors.lastname: Hardham
authors.forename: S J
authors.initials: SJ
authors.lastname: Norris
authors.forename: F C
authors.initials: FC
authors.lastname: Gherardini
mesh_terms: D001426:Bacterial Proteins; D001483:Base Sequence; D018983:DNA Footprinting; D015964:Gene Expression Regulation, Bacterial; D008345:Manganese / Q000378:metabolism* / Q000494:pharmacology; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009875:Operator Regions, Genetic; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011994:Recombinant Proteins / Q000302:isolation & purification; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic; D014210:Treponema pallidum / Q000737:chemistry* / Q000472:pathogenicity
chemical_list: D001426:Bacterial Proteins; D011994:Recombinant Proteins; D012097:Repressor Proteins; C121664:TroR protein, Treponema pallidum; D008345:Manganese