Characterization of a manganese-dependent regulatory protein, TroR, from Treponema pallidum.
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+).[1]References
- Characterization of a manganese-dependent regulatory protein, TroR, from Treponema pallidum. Posey, J.E., Hardham, J.M., Norris, S.J., Gherardini, F.C. Proc. Natl. Acad. Sci. U.S.A. (1999) [Pubmed]
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