1
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Jiang S, Steup LC, Kippnich C, Lazaridi S, Malengo G, Lemmin T, Yuan J. The inhibitory mechanism of a small protein reveals its role in antimicrobial peptide sensing. Proc Natl Acad Sci U S A 2023; 120:e2309607120. [PMID: 37792514 PMCID: PMC10576120 DOI: 10.1073/pnas.2309607120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 09/06/2023] [Indexed: 10/06/2023] Open
Abstract
A large number of small membrane proteins have been uncovered in bacteria, but their mechanism of action has remained mostly elusive. Here, we investigate the mechanism of a physiologically important small protein, MgrB, which represses the activity of the sensor kinase PhoQ and is widely distributed among enterobacteria. The PhoQ/PhoP two-component system is a master regulator of the bacterial virulence program and interacts with MgrB to modulate bacterial virulence, fitness, and drug resistance. A combination of cross-linking approaches with functional assays and protein dynamic simulations revealed structural rearrangements due to interactions between MgrB and PhoQ near the membrane/periplasm interface and along the transmembrane helices. These interactions induce the movement of the PhoQ catalytic domain and the repression of its activity. Without MgrB, PhoQ appears to be much less sensitive to antimicrobial peptides, including the commonly used C18G. In the presence of MgrB, C18G promotes MgrB to dissociate from PhoQ, thus activating PhoQ via derepression. Our findings reveal the inhibitory mechanism of the small protein MgrB and uncover its importance in antimicrobial peptide sensing.
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Affiliation(s)
- Shan Jiang
- Max Planck Institute for Terrestrial Microbiology, 35043Marburg, Germany
- Center for Synthetic Microbiology, 35043Marburg, Germany
| | - Lydia C. Steup
- Max Planck Institute for Terrestrial Microbiology, 35043Marburg, Germany
- Center for Synthetic Microbiology, 35043Marburg, Germany
| | - Charlotte Kippnich
- Max Planck Institute for Terrestrial Microbiology, 35043Marburg, Germany
- Center for Synthetic Microbiology, 35043Marburg, Germany
| | - Symela Lazaridi
- Institute of Biochemistry and Molecular Medicine, Faculty of Medicine, University of Bern, 3012Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, 3012Bern, Switzerland
| | - Gabriele Malengo
- Max Planck Institute for Terrestrial Microbiology, 35043Marburg, Germany
- Center for Synthetic Microbiology, 35043Marburg, Germany
| | - Thomas Lemmin
- Institute of Biochemistry and Molecular Medicine, Faculty of Medicine, University of Bern, 3012Bern, Switzerland
| | - Jing Yuan
- Max Planck Institute for Terrestrial Microbiology, 35043Marburg, Germany
- Center for Synthetic Microbiology, 35043Marburg, Germany
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2
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Choi J, Salvail H, Groisman EA. RNA chaperone activates Salmonella virulence program during infection. Nucleic Acids Res 2021; 49:11614-11628. [PMID: 34751407 PMCID: PMC8599858 DOI: 10.1093/nar/gkab992] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 10/04/2021] [Accepted: 10/18/2021] [Indexed: 11/17/2022] Open
Abstract
Organisms often harbor seemingly redundant proteins. In the bacterium Salmonella enterica serovar Typhimurium (S. Typhimurium), the RNA chaperones CspC and CspE appear to play redundant virulence roles because a mutant lacking both chaperones is attenuated, whereas mutants lacking only one exhibit wild-type virulence. We now report that CspC—but not CspE—is necessary to activate the master virulence regulator PhoP when S. Typhimurium experiences mildly acidic pH, such as inside macrophages. This CspC-dependent PhoP activation is specific to mildly acidic pH because a cspC mutant behaves like wild-type S. Typhimurium under other PhoP-activating conditions. Moreover, it is mediated by ugtL, a virulence gene required for PhoP activation inside macrophages. Purified CspC promotes ugtL translation by disrupting a secondary structure in the ugtL mRNA that occludes ugtL’s ribosome binding site. Our findings demonstrate that proteins that are seemingly redundant actually confer distinct and critical functions to the lifestyle of an organism.
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Affiliation(s)
- Jeongjoon Choi
- Department of Microbial Pathogenesis, Yale School of Medicine, 295 Congress Avenue, New Haven, CT 06536, USA
| | - Hubert Salvail
- Department of Microbial Pathogenesis, Yale School of Medicine, 295 Congress Avenue, New Haven, CT 06536, USA
| | - Eduardo A Groisman
- Department of Microbial Pathogenesis, Yale School of Medicine, 295 Congress Avenue, New Haven, CT 06536, USA.,Yale Microbial Sciences Institute, P.O. Box 27389, West Haven, CT 06516, USA
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3
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Cain AK, Boinett CJ, Barquist L, Dordel J, Fookes M, Mayho M, Ellington MJ, Goulding D, Pickard D, Wick RR, Holt KE, Parkhill J, Thomson NR. Morphological, genomic and transcriptomic responses of Klebsiella pneumoniae to the last-line antibiotic colistin. Sci Rep 2018; 8:9868. [PMID: 29959380 PMCID: PMC6026146 DOI: 10.1038/s41598-018-28199-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 06/08/2018] [Indexed: 11/09/2022] Open
Abstract
Colistin remains one of the few antibiotics effective against multi-drug resistant (MDR) hospital pathogens, such as Klebsiella pneumoniae. Yet resistance to this last-line drug is rapidly increasing. Characterized mechanisms of colR in K. pneumoniae are largely due to chromosomal mutations in two-component regulators, although a plasmid-mediated colR mechanism has recently been uncovered. However, the effects of intrinsic colistin resistance are yet to be characterized on a whole-genome level. Here, we used a genomics-based approach to understand the mechanisms of adaptive colR acquisition in K. pneumoniae. In controlled directed-evolution experiments we observed two distinct paths to colistin resistance acquisition. Whole genome sequencing identified mutations in two colistin resistance genes: in the known colR regulator phoQ which became fixed in the population and resulted in a single amino acid change, and unstable minority variants in the recently described two-component sensor crrB. Through RNAseq and microscopy, we reveal the broad range of effects that colistin exposure has on the cell. This study is the first to use genomics to identify a population of minority variants with mutations in a colR gene in K. pneumoniae.
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Affiliation(s)
- Amy K Cain
- Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, CB10 1SA, UK. .,Chemistry and Biomolecular Sciences, Macquarie University, Sydney, Australia.
| | - Christine J Boinett
- Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, CB10 1SA, UK. .,Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam.
| | - Lars Barquist
- Helmholtz Institute for RNA-based Infection Research, Würzburg, D-97080, Germany
| | - Janina Dordel
- Department of Biology, Drexel University, Philadelphia, 19104, PA, USA
| | - Maria Fookes
- Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, CB10 1SA, UK
| | - Matthew Mayho
- Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, CB10 1SA, UK
| | | | - David Goulding
- Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, CB10 1SA, UK
| | - Derek Pickard
- Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, CB10 1SA, UK
| | - Ryan R Wick
- Centre for Systems Genomics, The University of Melbourne, Melbourne, VIC, Australia
| | - Kathryn E Holt
- Centre for Systems Genomics, The University of Melbourne, Melbourne, VIC, Australia.,Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, VIC, Australia
| | - Julian Parkhill
- Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, CB10 1SA, UK
| | - Nicholas R Thomson
- Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, CB10 1SA, UK. .,Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom.
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4
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Choi J, Groisman EA. Activation of master virulence regulator PhoP in acidic pH requires the Salmonella-specific protein UgtL. Sci Signal 2017; 10:10/494/eaan6284. [PMID: 28851823 DOI: 10.1126/scisignal.aan6284] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Acidic conditions, such as those inside phagosomes, stimulate the intracellular pathogen Salmonella enterica to activate virulence genes. The sensor PhoQ responds to a mildly acidic pH by phosphorylating, and thereby activating, the virulence regulator PhoP. This PhoP/PhoQ two-component system is conserved in a subset of Gram-negative bacteria. PhoQ is thought to be sufficient to activate PhoP in mildly acidic pH. However, we found that the Salmonella-specific protein UgtL, which was horizontally acquired by Salmonella before the divergence of S. enterica and Salmonella bongori, was also necessary for PhoQ to activate PhoP under mildly acidic pH conditions but not for PhoQ to activate PhoP in response to low Mg2+ or the antimicrobial peptide C18G. UgtL increased the abundance of phosphorylated PhoP by stimulating autophosphorylation of PhoQ, thereby increasing the amount of the phosphodonor for PhoP. Deletion of ugtL attenuated Salmonella virulence and further reduced PhoP activation in a strain bearing a form of PhoQ that is not responsive to acidic pH. These data suggest that when Salmonella experiences mildly acidic pH, PhoP activation requires PhoQ to detect pH and UgtL to amplify the PhoQ response. Our findings reveal how acquisition of a foreign gene can strengthen signal responsiveness in an ancestral regulatory system.
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Affiliation(s)
- Jeongjoon Choi
- Department of Microbial Pathogenesis, Yale School of Medicine, 295 Congress Avenue, New Haven, CT 06536, USA
| | - Eduardo A Groisman
- Department of Microbial Pathogenesis, Yale School of Medicine, 295 Congress Avenue, New Haven, CT 06536, USA. .,Yale Microbial Sciences Institute, P.O. Box 27389, West Haven, CT 06516, USA
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5
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Abstract
This review reviews the properties and regulation of the Salmonella enterica serovar Typhimurium and Escherichia coli transporters that mediate Mg2+ influx: CorA and the Mgt P-type ATPases. In addition, potential Mg2+ regulation of transcription and translation, largely via the PhoPQ two component system, is discussed. CorA proteins are a unique class of transporters and are widespread in the Bacteria and Archaea, with rather distant but functional homologs in eukaryotes. The Mgt transporters are highly homologous to other P-type ATPases but are more closely related to the eukaryotic H+ and Ca2+ ATPases than to most prokaryotic ATPases. Hundreds of homologs of CorA are currently known from genomic sequencing. In contrast, only when extracellular and possibly intracellular Mg2+ levels fall significantly is the expression of mgtA and mgtB induced. Topology studies using blaM and lacZ fusions initially indicated that the Salmonella serovar Typhimurium CorA contained three transmembrane (TM) segments; however, subsequent data obtained using a variety of approaches showed that the CorA superfamily of proteins have only two TMs at the extreme C terminus. PhoP-PhoQ is a two-component system consisting of PhoQ, the sensor/receptor histidine kinase, and PhoP, the response regulator/transcriptional activator. The expression of both mgtA and mgtCB in either E. coli or Salmonella serovar Typhimurium is markedly induced in a PhoPQ-dependent manner by low concentrations of Mg2+ in the medium. phoP and phoQ form an operon with two promoters in both E. coli and Salmonella serovar Typhimurium.
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HAMP Domain Rotation and Tilting Movements Associated with Signal Transduction in the PhoQ Sensor Kinase. mBio 2015; 6:e00616-15. [PMID: 26015499 PMCID: PMC4447245 DOI: 10.1128/mbio.00616-15] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
HAMP domains are α-helical coiled coils that often transduce signals from extracytoplasmic sensing domains to cytoplasmic domains. Limited structural information has resulted in hypotheses that specific HAMP helix movement changes downstream enzymatic activity. These hypotheses were tested by mutagenesis and cysteine cross-linking analysis of the PhoQ histidine kinase, essential for resistance to antimicrobial peptides in a variety of enteric pathogens. These results support a mechanistic model in which periplasmic signals which induce an activation state generate a rotational movement accompanied by a tilt in α-helix 1 which activates kinase activity. Biochemical data and a high-confidence model of the PhoQ cytoplasmic domain indicate a possible physical interaction of the HAMP domain with the catalytic domain as necessary for kinase repression. These results support a model of PhoQ activation in which changes in the periplasmic domain lead to conformational movements in the HAMP domain helices which disrupt interaction between the HAMP and the catalytic domains, thus promoting increased kinase activity. Most studies on the HAMP domain signaling states have been performed with chemoreceptors or the HAMP domain of Af1503. Full-length structures of the HAMP-containing histidine kinases VicK and CpxA or a hybrid between the HAMP domain of Af1503 and the EnvZ histidine kinase agree with the parallel four-helix bundle structure identified in Af1503 and provide snapshots of structural conformations experienced by HAMP domains. We took advantage of the fact that we can easily regulate the activation state of PhoQ histidine kinase to study its HAMP domain in the context of the full-length protein in living cells and provide biochemical evidence for different conformational states experienced by Salmonella enterica serovar Typhimurium PhoQ HAMP domain upon signaling.
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7
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Hicks KG, Delbecq SP, Sancho-Vaello E, Blanc MP, Dove KK, Prost LR, Daley ME, Zeth K, Klevit RE, Miller SI. Acidic pH and divalent cation sensing by PhoQ are dispensable for systemic salmonellae virulence. eLife 2015; 4:e06792. [PMID: 26002083 PMCID: PMC4473727 DOI: 10.7554/elife.06792] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2015] [Accepted: 05/22/2015] [Indexed: 12/30/2022] Open
Abstract
Salmonella PhoQ is a histidine kinase with a periplasmic sensor domain (PD) that promotes virulence by detecting the macrophage phagosome. PhoQ activity is repressed by divalent cations and induced in environments of acidic pH, limited divalent cations, and cationic antimicrobial peptides (CAMP). Previously, it was unclear which signals are sensed by salmonellae to promote PhoQ-mediated virulence. We defined conformational changes produced in the PhoQ PD on exposure to acidic pH that indicate structural flexibility is induced in α-helices 4 and 5, suggesting this region contributes to pH sensing. Therefore, we engineered a disulfide bond between W104C and A128C in the PhoQ PD that restrains conformational flexibility in α-helices 4 and 5. PhoQW104C-A128C is responsive to CAMP, but is inhibited for activation by acidic pH and divalent cation limitation. phoQW104C-A128CSalmonella enterica Typhimurium is virulent in mice, indicating that acidic pH and divalent cation sensing by PhoQ are dispensable for virulence. DOI:http://dx.doi.org/10.7554/eLife.06792.001 Salmonella bacteria cause illnesses in humans, such as food poisoning and typhoid fever. In response to a Salmonella infection, immune cells known as macrophages detect and engulf the bacteria. The conditions inside the macrophage (which include an acidic pH and high levels of antimicrobial molecules) can destroy some bacteria. However, Salmonella bacteria (which are also called salmonellae) can sense and counteract these hostile conditions; this allows them to remodel their surface to survive and reproduce inside macrophages and continue to cause disease. A protein known as PhoQ, which is found on the surface of Salmonella bacteria, is a sensor that detects when the bacterium is inside a macrophage and so needs to boost its defenses. The PhoQ sensor is able to respond to acidity, the absence of divalent cations—such as magnesium and calcium ions—and certain antimicrobial peptide molecules. These conditions and components are used inside macrophages to try and kill the bacteria, but it was not known which of these signals PhoQ actually senses during an infection. Hicks et al. established how the sensor region of PhoQ changes when it is exposed to acid. This knowledge enabled variants of this protein to be constructed that do not respond when exposed to acidic conditions or low levels of divalent cations. Salmonellae that have these modified PhoQ sensors were still able to infect macrophages and cause disease in mice. These findings suggest that antimicrobial peptide sensing alone is sufficient to trigger the bacteria's defenses inside host organisms. Understanding how salmonellae detect antimicrobial factors could help with the development of new treatments for the diseases caused by these bacteria. Furthermore, the new tools developed by Hicks et al. could be applied to other systems to characterize how bacteria interact with their host environment during infection. DOI:http://dx.doi.org/10.7554/eLife.06792.002
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Affiliation(s)
- Kevin G Hicks
- Department of Microbiology, University of Washington Medical School, Seattle, United States
| | - Scott P Delbecq
- Department of Biochemistry, University of Washington Medical School, Seattle, United States
| | - Enea Sancho-Vaello
- Unidad de Biofisica, Centro Mixto Consejo Superior de Investigaciones Cientificas-Universidad del País Vasco/Euskal Herriko Unibertsitatea (CSIC,UPV/EHU), Leioa, Bizkaia, Spain
| | - Marie-Pierre Blanc
- Department of Microbiology, University of Washington Medical School, Seattle, United States
| | - Katja K Dove
- Department of Biochemistry, University of Washington Medical School, Seattle, United States
| | - Lynne R Prost
- Department of Biochemistry, University of Wisconsin-Madison, Madison, United States
| | - Margaret E Daley
- Department of Chemistry and Biochemistry, University of San Diego, San Diego, United States
| | - Kornelius Zeth
- Department of Biochemistry and Molecular Biology, University of Basque Country, Leioa, Spain
| | - Rachel E Klevit
- Department of Biochemistry, University of Washington Medical School, Seattle, United States
| | - Samuel I Miller
- Department of Microbiology, University of Washington Medical School, Seattle, United States
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8
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Eguchi Y, Ishii E, Yamane M, Utsumi R. The connector SafA interacts with the multi-sensing domain of PhoQ in Escherichia coli. Mol Microbiol 2012; 85:299-313. [DOI: 10.1111/j.1365-2958.2012.08114.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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9
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Antimicrobial peptides activate the Rcs regulon through the outer membrane lipoprotein RcsF. J Bacteriol 2010; 192:4894-903. [PMID: 20675476 DOI: 10.1128/jb.00505-10] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Salmonella enterica species are exposed to envelope stresses due to their environmental and infectious lifestyles. Such stresses include amphipathic cationic antimicrobial peptides (CAMPs), and resistance to these peptides is an important property for microbial virulence for animals. Bacterial mechanisms used to sense and respond to CAMP-induced envelope stress include the RcsFCDB phosphorelay, which contributes to survival from polymyxin B exposure. The Rcs phosphorelay includes two inner membrane (IM) proteins, RcsC and RcsD; the response regulator RcsB; the accessory coregulator RcsA; and an outer membrane bound lipoprotein, RcsF. Transcriptional activation of the Rcs regulon occurred within minutes of exposure to CAMP and during the first detectable signs of CAMP-induced membrane disorder. Rcs transcriptional activation by CAMPs required RcsF and preservation of its two internal disulfide linkages. The rerouting of RcsF to the inner membrane or its synthesis as an unanchored periplasmic protein resulted in constitutive activation of the Rcs regulon and RcsCD-dependent phosphorylation. These findings suggest that RcsFCDB activation in response to CAMP-induced membrane disorder is a result of a change in structure or availability of RcsF to the IM signaling constituents of the Rcs phosphorelay.
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10
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Strains of the East Asian (W/Beijing) lineage of Mycobacterium tuberculosis are DosS/DosT-DosR two-component regulatory system natural mutants. J Bacteriol 2010; 192:2228-38. [PMID: 20154135 DOI: 10.1128/jb.01597-09] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
As part of our ongoing efforts to uncover the phenotypic consequences of genetic variability among clinical Mycobacterium tuberculosis isolates, we previously reported that isolates of the "East Asian" or "W/Beijing" lineage constitutively overexpress the coordinately regulated transcriptional program known as the DosR regulon under standard in vitro conditions. This phenotype distinguishes the W/Beijing lineage from all other M. tuberculosis lineages, which normally induce expression of this regulon only once exposed to low oxygen or nitric oxide, both of which result in inhibition of bacterial respiration and replication. Transcription of the DosR regulon is controlled through a two-component regulatory system comprising the transcription factor DosR and two possible cognate histidine sensor kinases, DosS and DosT. Through sequence analysis of a carefully selected set of isolates representing each of the major M. tuberculosis lineages, we describe herein a naturally occurring frameshift mutation in the gene encoding the DosT sensor kinase for isolates of the most recently evolved W/Beijing sublineages. Intriguingly, the occurrence of the frameshift mutation correlates precisely with the appearance of the constitutive DosR regulon phenotype displayed by the same "modern" W/Beijing strains. However, complementation studies have revealed that the mutation in dosT alone is not directly responsible for the constitutive DosR regulon phenotype. Our data serve to highlight the evolutionary pressure that exists among distinct M. tuberculosis lineages to maintain tight control over DosR regulon expression.
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11
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Prost LR, Daley ME, Le Sage V, Bader MW, Le Moual H, Klevit RE, Miller SI. Activation of the Bacterial Sensor Kinase PhoQ by Acidic pH. Mol Cell 2007; 26:165-74. [PMID: 17466620 DOI: 10.1016/j.molcel.2007.03.008] [Citation(s) in RCA: 205] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2006] [Revised: 01/25/2007] [Accepted: 03/05/2007] [Indexed: 10/23/2022]
Abstract
The Salmonellae PhoQ sensor kinase senses the mammalian phagosome environment to activate a transcriptional program essential for virulence. The PhoQ periplasmic domain binds divalent cations, forming bridges with inner membrane phospholipids to maintain PhoQ repression. PhoQ also binds and is activated by cationic antimicrobial peptides. In this work, PhoQ is directly activated by exposure of the sensor domain to pH 5.5. NMR spectroscopy indicates that at acidic pH, the PhoQ periplasmic domain adopts a conformation different from that in the presence of divalent cations or antimicrobial peptides. The conformation is partially simulated by mutation of histidine 157, which is part of an interaction network that distinguishes the repressed conformation. The effects of antimicrobial peptides and pH on PhoQ activity are additive. We propose a model of activation by antimicrobial peptides via disruption of the cation bridges and/or by acidification of the periplasm through destabilization of the interaction network.
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Affiliation(s)
- Lynne R Prost
- Department of Microbiology, University of Washington Medical School, Seattle, WA 98195, USA
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12
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Perron-Savard P, De Crescenzo G, Moual HL. Dimerization and DNA binding of the Salmonella enterica PhoP response regulator are phosphorylation independent. MICROBIOLOGY-SGM 2006; 151:3979-3987. [PMID: 16339942 DOI: 10.1099/mic.0.28236-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In Salmonella enterica, PhoP is the response regulator of the PhoP/PhoQ two-component regulatory system that controls the expression of various virulence factors in response to external Mg2+. Previous studies have shown that phosphorylation of a PhoP variant with a C-terminal His tag (PhoP(His)) enhances dimerization and binding to target DNA. Here, the effect of phosphorylation on the oligomerization and DNA binding properties of both wild-type PhoP (PhoP) and PhoP(His) are compared. Gel filtration chromatography showed that PhoP exists as a mixture of monomer and dimer regardless of its phosphorylation state. In contrast, unphosphorylated PhoP(His) was mostly monomeric, whereas PhoP(His) approximately P existed as a mixture of monomer and dimer. By monitoring the tryptophan fluorescence of the proteins and the fluorescence of the probe 1-anilinonaphthalene-8-sulfonic acid bound to them, it was found that PhoP and PhoP(His) exhibited different spectral properties. The interaction between PhoP or PhoP(His) and the PhoP box of the mgtA promoter was monitored by surface plasmon resonance. Binding of PhoP to the PhoP box was barely influenced by phosphorylation. In contrast, phosphorylation of PhoP(His) clearly increased the interaction of PhoP(His) with target DNA. Altogether, these data show that a His tag at the C-terminus of PhoP affects its biochemical properties, most likely by affecting its conformation and/or its oligomerization state. More importantly, these results show that wild-type PhoP dimerization and interaction with target DNA are independent of phosphorylation, which is in contrast to the previously proposed model.
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Affiliation(s)
- Philippe Perron-Savard
- Department of Microbiology and Immunology, McGill University, Montréal, Québec, Canada H3A 2B4
| | - Gregory De Crescenzo
- Protein-Protein Interaction Facility, Sheldon Biotechnology Centre, McGill University, Montréal, Québec, Canada H3A 2B4
| | - Hervé Le Moual
- Faculty of Dentistry, McGill University, Montréal, Québec, Canada H3A 2B4
- Department of Microbiology and Immunology, McGill University, Montréal, Québec, Canada H3A 2B4
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Sanowar S, Le Moual H. Functional reconstitution of the Salmonella typhimurium PhoQ histidine kinase sensor in proteoliposomes. Biochem J 2006; 390:769-76. [PMID: 15910283 PMCID: PMC1199670 DOI: 10.1042/bj20050060] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Two-component signal-transduction systems are widespread in bacteria. They are usually composed of a transmembrane histidine kinase sensor and a cytoplasmic response regulator. The PhoP/PhoQ two-component system of Salmonella typhimurium contributes to virulence by co-ordinating the adaptation to low concentrations of environmental Mg2+. Limiting concentrations of extracellular Mg2+ activate the PhoP/PhoQ phosphorylation cascade modulating the transcription of PhoP-regulated genes. In contrast, high concentrations of extracellular Mg2+ stimulate the dephosphorylation of the response regulator PhoP by the PhoQ kinase sensor. In the present study, we report the purification and functional reconstitution of PhoQ(His), a PhoQ variant with a C-terminal His tag, into Escherichia coli liposomes. The functionality of PhoQ(His) was essentially similar to that of PhoQ as shown in vivo and in vitro. Purified PhoQ(His) was inserted into liposomes in a unidirectional orientation, with the sensory domain facing the lumen and the catalytic domain facing the extraluminal environment. Reconstituted PhoQ(His) exhibited all the catalytic activities that have been described for histidine kinase sensors. Reconstituted PhoQ(His) was capable of autokinase activity when incubated in the presence of Mg2+-ATP. The phosphoryl group could be transferred from reconstituted PhoQ(His) to PhoP. Reconstituted PhoQ(His) catalysed the dephosphorylation of phospho-PhoP and this activity was stimulated by the addition of extraluminal ADP.
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Affiliation(s)
- Sarah Sanowar
- Department of Microbiology and Immunology, McGill University, 3775 University Street, Montreal, Quebec, Canada H3A 2B4
| | - Hervé Le Moual
- Department of Microbiology and Immunology, McGill University, 3775 University Street, Montreal, Quebec, Canada H3A 2B4
- To whom correspondence should be addressed (email )
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14
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Cho US, Bader MW, Amaya MF, Daley ME, Klevit RE, Miller SI, Xu W. Metal bridges between the PhoQ sensor domain and the membrane regulate transmembrane signaling. J Mol Biol 2005; 356:1193-206. [PMID: 16406409 DOI: 10.1016/j.jmb.2005.12.032] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2005] [Revised: 12/07/2005] [Accepted: 12/11/2005] [Indexed: 10/25/2022]
Abstract
Bacterial histidine kinases respond to environmental stimuli by transducing a signal from an extracytosolic sensor domain to a cytosolic catalytic domain. Among them, PhoQ promotes bacterial virulence and is tightly repressed by the divalent cations such as calcium and magnesium. We have determined the crystal structure of the PhoQ sensor domain from Salmonella typhimurium in the Ca2+-bound state, which reveals a highly negatively charged surface that is in close proximity to the inner membrane. This acidic surface binds at least three Ca2+, which mediate the PhoQ-membrane interaction. Mutagenesis analysis indicates that structural integrity at the membrane proximal region of the PhoQ sensor domain promotes metal-mediated repression. We propose that depletion or displacement of divalent cations leads to charge repulsion between PhoQ and the membrane, which initiates transmembrane signaling through a change in orientation between the PhoQ sensor domain and membrane. Therefore, both PhoQ and the membrane are required for extracytosolic sensing and transmembrane signaling.
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Affiliation(s)
- Uhn Soo Cho
- Department of Biological Structure, University of Washington, Seattle, WA 98195, USA
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Hasegawa Y, Nishiyama SI, Nishikawa K, Kadowaki T, Yamamoto K, Noguchi T, Yoshimura F. A novel type of two-component regulatory system affecting gingipains in Porphyromonas gingivalis. Microbiol Immunol 2004; 47:849-58. [PMID: 14638996 DOI: 10.1111/j.1348-0421.2003.tb03451.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We surveyed the Porphyromonas gingivalis W83 genome database for homologues of FimS, the first two-component sensor histidine kinase, which could possibly control virulence factors. Including fimS, we found six putative sensor kinase genes in the genome. The gene encoding one of the homologues was cloned from a P. gingivalis plasmid library, sequenced, and analyzed using its mutants. Two gene-disruption mutants were created in strain ATCC 33277 by introducing a drug cassette into the gene. The mutants formed nonpigmented colonies, indicating that they might be defective in proteinase production, a characteristic of this organism. Proteinase activities, measured as arginine- and lysine-specific (Rgp and Kgp gingipains, respectively) activities, of the mutants were almost half those of the parent strain. Unlike the parent and wildtype strains, most of the gingipain activities were detected in the culture supernatant, not in cells, of the mutants. Abnormal production of gingipains was confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and Western blot analyses. These results strongly suggest that this newly-discovered two-component sensor kinase is involved in maturation and proper localization of gingipains to the outer membrane through an unknown mechanism. The gene encoding the sensor histidine kinase was designated gppX, which represents regulation (X) of gingipains and black pigmentation in P. gingivalis.
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Affiliation(s)
- Yoshiaki Hasegawa
- Department of Periodontology, School of Dentistry, Aichi-Gakuin University, Nagoya, Japan
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