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Publication Abstract from PubMed

Several Leptospira species cause leptospirosis, the most extended zoonosis worldwide. In bacteria, two-component systems constitute key signalling pathways, some of which are involved in pathogenesis. The physiological roles of two-component systems in Leptospira are largely unknown, despite identifying several dozens within their genomes. Biochemical confirmation of an operative phosphorelaying two-component system has been obtained so far only for the Hklep/Rrlep pair. It is known that hklep/rrlep knockout strains of Leptospira biflexa result in haem auxotrophy, although their de novo biosynthesis machinery remains fully functional. Haem is essential for Leptospira, but information about Hklep/Rrlep effector function(s) and target(s) is still lacking. We are now reporting a thorough molecular characterization of this system, which we rename HemK/HemR. The DNA HemR-binding motif was determined, and found within the genomes of saprophyte and pathogenic Leptospira. In this way, putative HemR-regulated genes were pinpointed, including haem catabolism-related (hmuO - haem oxygenase) and biosynthesis-related (the hemA/C/D/B/L/E/N/G operon). Specific HemR binding to these two promoters was quantified, and a dual function was observed in vivo, inversely repressing the hmuO, while activating the hemA operon transcription. The crystal structure of HemR receiver domain was determined, leading to a mechanistic model for its dual regulatory role.

HemR is an OmpR/PhoB-like response regulator from Leptospira, which simultaneously effects transcriptional activation and repression of key haem metabolism genes.,Morero NR, Botti H, Nitta KR, Carrion F, Obal G, Picardeau M, Buschiazzo A Mol Microbiol. 2014 Oct;94(2):340-52. doi: 10.1111/mmi.12763. Epub 2014 Sep 15. PMID:25145397^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.