The Mannitol Operon Repressor MTIR belongs to a new class of transcription regulators in bacteria.
- Biosciences Division
Many bacteria express phosphoenolpyruvate-dependent phosphotransferase systems (PTS). The mannitol-specific PTS catalyze the uptake and phosphorylation of d-mannitol. The uptake system comprises several genes encoded in the single operon. The expression of the mannitol operon is regulated by a proposed transcriptional factor, mannitol operon repressor (MtlR) that was first studied in Escherichia coli. Here we report the first crystal structures of MtlR from Vibrio parahemeolyticus (Vp-MtlR) and its homolog YggD protein from Shigella flexneri (Sf-YggD). MtlR and YggD belong to the same protein family (Pfam05068). Although Vp-MtlR and Sf-YggD share low sequence identity (22%), their overall structures are very similar, representing a novel all {alpha}-helical fold, and indicate similar function. However, their lack of any known DNA-binding structural motifs and their unfavorable electrostatic properties imply that MtlR/YggD are unlikely to bind a specific DNA operator directly as proposed earlier. This structural observation is further corroborated by in vitro DNA-binding studies of E. coli MtlR (Ec-MtlR), which detected no interaction of Ec-MtlR with the well characterized mannitol operator/promoter region. Therefore, MtlR/YggD belongs to a new class of transcription factors in bacteria that may regulate gene expression indirectly as a part of a larger transcriptional complex.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC); National Institutes of Health (NIH)
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 1047437
- Report Number(s):
- ANL/BIO/JA-66880; JBCHA3; TRN: US201216%%285
- Journal Information:
- Journal of Biological Chemistry, Vol. 284, Issue 52; ISSN 0021-9258
- Country of Publication:
- United States
- Language:
- ENGLISH
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