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Structural basis of the signalling through a bacterial membrane receptor HasR deciphered by an integrative approach. Biochem J 2016; 473:2239-48. [PMID: 27208170 PMCID: PMC4941744 DOI: 10.1042/bcj20160131] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 05/13/2016] [Indexed: 01/19/2023]
Abstract
In bacteria, some scarce nutrients are sensed, bound and internalized by their specific transporter. In the present study, using an integrative structural approach, we study HasR, a bacterial haem transporter in both its free and its loaded forms. Bacteria use diverse signalling pathways to adapt gene expression to external stimuli. In Gram-negative bacteria, the binding of scarce nutrients to membrane transporters triggers a signalling process that up-regulates the expression of genes of various functions, from uptake of nutrient to production of virulence factors. Although proteins involved in this process have been identified, signal transduction through this family of transporters is not well understood. In the present study, using an integrative approach (EM, SAXS, X-ray crystallography and NMR), we have studied the structure of the haem transporter HasR captured in two stages of the signalling process, i.e. before and after the arrival of signalling activators (haem and its carrier protein). We show for the first time that the HasR domain responsible for signal transfer: (i) is highly flexible in two stages of signalling; (ii) extends into the periplasm at approximately 70–90 Å (1 Å=0.1 nm) from the HasR β-barrel; and (iii) exhibits local conformational changes in response to the arrival of signalling activators. These features would favour the signal transfer from HasR to its cytoplasmic membrane partners.
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Malki I, Simenel C, Wojtowicz H, Cardoso de Amorim G, Prochnicka-Chalufour A, Hoos S, Raynal B, England P, Chaffotte A, Delepierre M, Delepelaire P, Izadi-Pruneyre N. Interaction of a partially disordered antisigma factor with its partner, the signaling domain of the TonB-dependent transporter HasR. PLoS One 2014; 9:e89502. [PMID: 24727671 PMCID: PMC3984077 DOI: 10.1371/journal.pone.0089502] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 01/21/2014] [Indexed: 11/21/2022] Open
Abstract
Bacteria use diverse signaling pathways to control gene expression in response to external stimuli. In Gram-negative bacteria, the binding of a nutrient is sensed by an outer membrane transporter. This signal is then transmitted to an antisigma factor and subsequently to the cytoplasm where an ECF sigma factor induces expression of genes related to the acquisition of this nutrient. The molecular interactions involved in this transmembrane signaling are poorly understood and structural data on this family of antisigma factor are rare. Here, we present the first structural study of the periplasmic domain of an antisigma factor and its interaction with the transporter. The study concerns the signaling in the heme acquisition system (Has) of Serratia marcescens. Our data support unprecedented partially disordered periplasmic domain of an anti-sigma factor HasS in contact with a membrane-mimicking environment. We solved the 3D structure of the signaling domain of HasR transporter and identified the residues at the HasS-HasR interface. Their conservation in several bacteria suggests wider significance of the proposed model for the understanding of bacterial transmembrane signaling.
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Affiliation(s)
- Idir Malki
- Institut Pasteur, Unité de RMN des Biomolécules, Département de Biologie Structurale et Chimie, Paris, France
- CNRS, UMR 3528, Paris, France
- Université Pierre et Marie Curie, Cellule Pasteur UPMC, Paris, France
| | - Catherine Simenel
- Institut Pasteur, Unité de RMN des Biomolécules, Département de Biologie Structurale et Chimie, Paris, France
- CNRS, UMR 3528, Paris, France
| | - Halina Wojtowicz
- Institut Pasteur, Unité de RMN des Biomolécules, Département de Biologie Structurale et Chimie, Paris, France
- CNRS, UMR 3528, Paris, France
| | - Gisele Cardoso de Amorim
- Institut Pasteur, Unité de RMN des Biomolécules, Département de Biologie Structurale et Chimie, Paris, France
- CNRS, UMR 3528, Paris, France
| | - Ada Prochnicka-Chalufour
- Institut Pasteur, Unité de RMN des Biomolécules, Département de Biologie Structurale et Chimie, Paris, France
- CNRS, UMR 3528, Paris, France
| | - Sylviane Hoos
- Institut Pasteur, Plate-forme de Biophysique des Macromolécules et de leurs Interactions, Département de Biologie Structurale et Chimie, Paris, France
| | - Bertrand Raynal
- Institut Pasteur, Plate-forme de Biophysique des Macromolécules et de leurs Interactions, Département de Biologie Structurale et Chimie, Paris, France
| | - Patrick England
- Institut Pasteur, Plate-forme de Biophysique des Macromolécules et de leurs Interactions, Département de Biologie Structurale et Chimie, Paris, France
| | - Alain Chaffotte
- Institut Pasteur, Unité de RMN des Biomolécules, Département de Biologie Structurale et Chimie, Paris, France
- CNRS, UMR 3528, Paris, France
| | - Muriel Delepierre
- Institut Pasteur, Unité de RMN des Biomolécules, Département de Biologie Structurale et Chimie, Paris, France
- CNRS, UMR 3528, Paris, France
| | - Philippe Delepelaire
- Institut de Biologie Physico-Chimique, CNRS Université Paris-Diderot UMR 7099, Paris, France
| | - Nadia Izadi-Pruneyre
- Institut Pasteur, Unité de RMN des Biomolécules, Département de Biologie Structurale et Chimie, Paris, France
- CNRS, UMR 3528, Paris, France
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Contreras H, Chim N, Credali A, Goulding CW. Heme uptake in bacterial pathogens. Curr Opin Chem Biol 2014; 19:34-41. [PMID: 24780277 DOI: 10.1016/j.cbpa.2013.12.014] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Revised: 12/12/2013] [Accepted: 12/12/2013] [Indexed: 11/30/2022]
Abstract
Iron is an essential nutrient for the survival of organisms. Bacterial pathogens possess specialized pathways to acquire heme from their human hosts. In this review, we present recent structural and biochemical data that provide mechanistic insights into several bacterial heme uptake pathways, encompassing the sequestration of heme from human hemoproteins to secreted or membrane-associated bacterial proteins, the transport of heme across bacterial membranes, and the degradation of heme within the bacterial cytosol to liberate iron. The pathways for heme transport into the bacterial cytosol are divergent, harboring non-homologous protein sequences, novel structures, varying numbers of proteins, and different mechanisms. Congruously, the breakdown of heme within the bacterial cytosol by sequence-divergent proteins releases iron and distinct degradation products.
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Affiliation(s)
- Heidi Contreras
- Department of Molecular Biology and Biochemistry, UCI, Irvine, CA 92697, USA
| | - Nicholas Chim
- Department of Molecular Biology and Biochemistry, UCI, Irvine, CA 92697, USA
| | - Alfredo Credali
- Department of Molecular Biology and Biochemistry, UCI, Irvine, CA 92697, USA
| | - Celia W Goulding
- Department of Molecular Biology and Biochemistry, UCI, Irvine, CA 92697, USA; Department of Pharmaceutical Sciences, UCI, Irvine, CA 92697, USA.
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