title: HemR is an OmpR/PhoB-like response regulator from Leptospira, which simultaneously effects transcriptional activation and repression of key haem metabolism genes.
abstract: 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.
authors.affiliation: Institut Pasteur de Montevideo, Unit of Protein Crystallography, 2020 Mataojo, 11400, Montevideo, Uruguay.
authors.forename: Natalia R
authors.initials: NR
authors.lastname: Morero
authors.forename: Horacio
authors.initials: H
authors.lastname: Botti
authors.forename: Kazuhiro R
authors.initials: KR
authors.lastname: Nitta
authors.forename: Federico
authors.initials: F
authors.lastname: Carrión
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Obal
authors.forename: Mathieu
authors.initials: M
authors.lastname: Picardeau
authors.forename: Alejandro
authors.initials: A
authors.lastname: Buschiazzo
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D006418:Heme / Q000378:metabolism*; D007919:Leptospira / Q000235:genetics* / Q000378:metabolism*; D053858:Metabolic Networks and Pathways / Q000235:genetics*; D008958:Models, Molecular; D009876:Operon; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011487:Protein Conformation; D018085:Regulon; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D004269:DNA, Bacterial; D014157:Transcription Factors; D006418:Heme