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Patino R, Kühn MJ, Macmillan H, Inclan YF, Chavez I, Von Dollen J, Johnson JR, Swaney DL, Krogan NJ, Persat A, Engel JN. Spatial control of sensory adaptation modulates mechanosensing in Pseudomonas aeruginosa. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.27.582188. [PMID: 38464290 PMCID: PMC10925122 DOI: 10.1101/2024.02.27.582188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2024]
Abstract
Sensory signaling pathways use adaptation to dynamically respond to changes in their environment. Here, we report the mechanism of sensory adaptation in the Pil-Chp mechanosensory system, which the important human pathogen Pseudomonas aeruginosa uses to sense mechanical stimuli during surface exploration. Using biochemistry, genetics, and cell biology, we discovered that the enzymes responsible for adaptation, a methyltransferase and a methylesterase, are segregated to opposing cell poles as P. aeruginosa explore surfaces. By coordinating the localization of both enzymes, we found that the Pil-Chp response regulators influence local receptor methylation, the molecular basis of bacterial sensory adaptation. We propose a model in which adaptation during mechanosensing spatially resets local receptor methylation, and thus Pil-Chp signaling, to modulate the pathway outputs, which are involved in P. aeruginosa virulence. Despite decades of bacterial sensory adaptation studies, our work has uncovered an unrecognized mechanism that bacteria use to achieve adaptation to sensory stimuli.
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Uchida Y, Hamamoto T, Che YS, Takahashi H, Parkinson JS, Ishijima A, Fukuoka H. The Chemoreceptor Sensory Adaptation System Produces Coordinated Reversals of the Flagellar Motors on an Escherichia coli Cell. J Bacteriol 2022; 204:e0027822. [PMID: 36448786 PMCID: PMC9765175 DOI: 10.1128/jb.00278-22] [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: 07/21/2022] [Accepted: 11/01/2022] [Indexed: 12/05/2022] Open
Abstract
In isotropic environments, an Escherichia coli cell exhibits coordinated rotational switching of its flagellar motors, produced by fluctuations in the intracellular concentration of phosphorylated CheY (CheY-P) emanating from chemoreceptor signaling arrays. In this study, we show that these CheY-P fluctuations arise through modifications of chemoreceptors by two sensory adaptation enzymes: the methyltransferase CheR and the methylesterase CheB. A cell containing CheR, CheB, and the serine chemoreceptor Tsr exhibited motor synchrony, whereas a cell lacking CheR and CheB or containing enzymatically inactive forms did not. Tsr variants with different combinations of methylation-mimicking Q residues at the adaptation sites also failed to show coordinated motor switching in cells lacking CheR and CheB. Cells containing CheR, CheB, and Tsr [NDND], a variant in which the adaptation site residues are not substrates for CheR or CheB modifications, also lacked motor synchrony. TsrΔNWETF, which lacks a C-terminal pentapeptide-binding site for CheR and CheB, and the ribose-galactose receptor Trg, which natively lacks this motif, failed to produce coordinated motor switching, despite the presence of CheR and CheB. However, addition of the NWETF sequence to Trg enabled Trg-NWETF to produce motor synchrony, as the sole receptor type in cells containing CheR and CheB. Finally, CheBc, the catalytic domain of CheB, supported motor coordination in combination with CheR and Tsr. These results indicate that the coordination of motor switching requires CheR/CheB-mediated changes in receptor modification state. We conclude that the opposing receptor substrate-site preferences of CheR and CheB produce spontaneous blinking of the chemoreceptor array's output activity. IMPORTANCE Under steady-state conditions with no external stimuli, an Escherichia coli cell coordinately switches the rotational direction of its flagellar motors. Here, we demonstrate that the CheR and CheB enzymes of the chemoreceptor sensory adaptation system mediate this coordination. Stochastic fluctuations in receptor adaptation states trigger changes in signal output from the receptor array, and this array blinking generates fluctuations in CheY-P concentration that coordinate directional switching of the flagellar motors. Thus, in the absence of chemoeffector gradients, the sensory adaptation system controls run-tumble swimming of the cell, its optimal foraging strategy.
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Affiliation(s)
- Yumiko Uchida
- Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
| | - Tatsuki Hamamoto
- Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
| | - Yong-Suk Che
- Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
| | - Hiroto Takahashi
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Miyagi, Japan
| | - John S. Parkinson
- School of Biological Sciences, University of Utah, Salt Lake City, Utah, USA
| | - Akihiko Ishijima
- Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
| | - Hajime Fukuoka
- Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
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Padilla-Vaca F, Vargas-Maya NI, Elizarrarás-Vargas NU, Rangel-Serrano Á, Cardoso-Reyes LR, Razo-Soria T, Membrillo-Hernández J, Franco B. Flotillin homologue is involved in the swimming behavior of Escherichia coli. Arch Microbiol 2019; 201:999-1008. [PMID: 31062059 DOI: 10.1007/s00203-019-01670-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 04/22/2019] [Accepted: 04/24/2019] [Indexed: 01/22/2023]
Abstract
Cellular membrane is a key component for maintaining cell shape and integrity. The classical membrane structure and function by Singer and Nicolson groundbreaking model has depicted the membrane as a homogeneous fluid structure. This view has changed by the discovery of discrete domains containing different lipid compositions, called lipid rafts, which play a key role in signal transduction in eukaryotic cells. In the past few years, lipid raft-like structures have been found in bacteria also, constituted by cardiolipin and other modified lipids, perhaps involved in generating a specific site for protein clustering. Here, we report the analysis of a protein termed YqiK from Escherichia coli, a prohibitin homolog that has been implicated in stress sensing by the formation of membrane-associated microdomains. The E. coli yqiK-deficient mutant strain showed an enhanced swimming behavior and was resistant to ampicillin but its response to other stressing conditions was similar to that of the wild-type strain. The abnormal swimming behavior is reversed when the protein is expressed in trans from a plasmid. Also, we demonstrate that YqiK is not redundant with QmcA, another flotillin homolog found in E. coli. Our results, along with the data available in the literature, suggest that YqiK may be involved in the formation of discrete membrane-associated signaling complexes that regulate and agglomerate signaling proteins to generate cell response to chemotaxis.
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Affiliation(s)
- Felipe Padilla-Vaca
- División de Ciencias Naturales y Exactas, Departamento de Biología, Universidad de Guanajuato, Noria Alta s/n, Guanajuato, Gto, 36050, Mexico
| | - Naurú Idalia Vargas-Maya
- División de Ciencias Naturales y Exactas, Departamento de Biología, Universidad de Guanajuato, Noria Alta s/n, Guanajuato, Gto, 36050, Mexico
| | - Narciso Ulises Elizarrarás-Vargas
- División de Ciencias Naturales y Exactas, Departamento de Biología, Universidad de Guanajuato, Noria Alta s/n, Guanajuato, Gto, 36050, Mexico
| | - Ángeles Rangel-Serrano
- División de Ciencias Naturales y Exactas, Departamento de Biología, Universidad de Guanajuato, Noria Alta s/n, Guanajuato, Gto, 36050, Mexico
| | - Luis Rafael Cardoso-Reyes
- División de Ciencias Naturales y Exactas, Departamento de Biología, Universidad de Guanajuato, Noria Alta s/n, Guanajuato, Gto, 36050, Mexico
| | - Tannia Razo-Soria
- División de Ciencias Naturales y Exactas, Departamento de Biología, Universidad de Guanajuato, Noria Alta s/n, Guanajuato, Gto, 36050, Mexico
| | - Jorge Membrillo-Hernández
- Departamento de Bioingeniería, Escuela de Ingeniería y Ciencias, Tecnológico de Monterrey, Monterrey, Mexico
| | - Bernardo Franco
- División de Ciencias Naturales y Exactas, Departamento de Biología, Universidad de Guanajuato, Noria Alta s/n, Guanajuato, Gto, 36050, Mexico.
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Hiremath G, Hyakutake A, Yamamoto K, Ebisawa T, Nakamura T, Nishiyama SI, Homma M, Kawagishi I. Hypoxia-induced localization of chemotaxis-related signaling proteins inVibrio cholerae. Mol Microbiol 2015; 95:780-90. [DOI: 10.1111/mmi.12887] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/21/2014] [Indexed: 11/29/2022]
Affiliation(s)
- Geetha Hiremath
- Research Center for Micro-Nano Technology; Hosei University; Koganei Tokyo 184-8584 Japan
| | - Akihiro Hyakutake
- Division of Biological Science; Graduate School of Science; Nagoya University; Chikusa-ku Nagoya 464-8602 Japan
| | - Kentaro Yamamoto
- Department of Frontier Bioscience; Hosei University; Koganei Tokyo 184-8584 Japan
| | - Tatsuaki Ebisawa
- Department of Frontier Bioscience; Hosei University; Koganei Tokyo 184-8584 Japan
| | - Tomoyuki Nakamura
- Department of Frontier Bioscience; Hosei University; Koganei Tokyo 184-8584 Japan
| | - So-ichiro Nishiyama
- Department of Frontier Bioscience; Hosei University; Koganei Tokyo 184-8584 Japan
| | - Michio Homma
- Division of Biological Science; Graduate School of Science; Nagoya University; Chikusa-ku Nagoya 464-8602 Japan
| | - Ikuro Kawagishi
- Research Center for Micro-Nano Technology; Hosei University; Koganei Tokyo 184-8584 Japan
- Department of Frontier Bioscience; Hosei University; Koganei Tokyo 184-8584 Japan
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Abstract
The bacterial strategy of chemotaxis relies on temporal comparisons of chemical concentrations, where the probability of maintaining the current direction of swimming is modulated by changes in stimulation experienced during the recent past. A short-term memory required for such comparisons is provided by the adaptation system, which operates through the activity-dependent methylation of chemotaxis receptors. Previous theoretical studies have suggested that efficient navigation in gradients requires a well-defined adaptation rate, because the memory time scale needs to match the duration of straight runs made by bacteria. Here we demonstrate that the chemotaxis pathway of Escherichia coli does indeed exhibit a universal relation between the response magnitude and adaptation time which does not depend on the type of chemical ligand. Our results suggest that this alignment of adaptation rates for different ligands is achieved through cooperative interactions among chemoreceptors rather than through fine-tuning of methylation rates for individual receptors. This observation illustrates a yet-unrecognized function of receptor clustering in bacterial chemotaxis.
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Cain JA, Solis N, Cordwell SJ. Beyond gene expression: the impact of protein post-translational modifications in bacteria. J Proteomics 2013; 97:265-86. [PMID: 23994099 DOI: 10.1016/j.jprot.2013.08.012] [Citation(s) in RCA: 136] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Revised: 07/08/2013] [Accepted: 08/10/2013] [Indexed: 12/12/2022]
Abstract
The post-translational modification (PTM) of proteins plays a critical role in the regulation of a broad range of cellular processes in eukaryotes. Yet their role in governing similar systems in the conventionally presumed 'simpler' forms of life has been largely neglected and, until recently, was thought to occur only rarely, with some modifications assumed to be limited to higher organisms alone. Recent developments in mass spectrometry-based proteomics have provided an unparalleled power to enrich, identify and quantify peptides with PTMs. Additional modifications to biological molecules such as lipids and carbohydrates that are essential for bacterial pathophysiology have only recently been detected on proteins. Here we review bacterial protein PTMs, focusing on phosphorylation, acetylation, proteolytic degradation, methylation and lipidation and the roles they play in bacterial adaptation - thus highlighting the importance of proteomic techniques in a field that is only just in its infancy. This article is part of a Special Issue entitled: Trends in Microbial Proteomics.
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Affiliation(s)
- Joel A Cain
- School of Molecular Bioscience, School of Medical Sciences, The University of Sydney, 2006, Australia
| | - Nestor Solis
- School of Molecular Bioscience, School of Medical Sciences, The University of Sydney, 2006, Australia
| | - Stuart J Cordwell
- School of Molecular Bioscience, School of Medical Sciences, The University of Sydney, 2006, Australia; Discipline of Pathology, School of Medical Sciences, The University of Sydney, 2006, Australia.
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Othmer HG, Xin X, Xue C. Excitation and adaptation in bacteria-a model signal transduction system that controls taxis and spatial pattern formation. Int J Mol Sci 2013; 14:9205-48. [PMID: 23624608 PMCID: PMC3676780 DOI: 10.3390/ijms14059205] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Revised: 03/20/2013] [Accepted: 03/22/2013] [Indexed: 11/16/2022] Open
Abstract
The machinery for transduction of chemotactic stimuli in the bacterium E. coli is one of the most completely characterized signal transduction systems, and because of its relative simplicity, quantitative analysis of this system is possible. Here we discuss models which reproduce many of the important behaviors of the system. The important characteristics of the signal transduction system are excitation and adaptation, and the latter implies that the transduction system can function as a "derivative sensor" with respect to the ligand concentration in that the DC component of a signal is ultimately ignored if it is not too large. This temporal sensing mechanism provides the bacterium with a memory of its passage through spatially- or temporally-varying signal fields, and adaptation is essential for successful chemotaxis. We also discuss some of the spatial patterns observed in populations and indicate how cell-level behavior can be embedded in population-level descriptions.
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Affiliation(s)
- Hans G. Othmer
- School of Mathematics, University of Minnesota, Minneapolis, MN 55455, USA; E-Mail:
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +612-624-8325; Fax: +612-626-2017
| | - Xiangrong Xin
- School of Mathematics, University of Minnesota, Minneapolis, MN 55455, USA; E-Mail:
| | - Chuan Xue
- Department of Mathematics, Ohio State University, Columbus, OH 43210, USA; E-Mail:
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Schulmeister S, Grosse K, Sourjik V. Effects of receptor modification and temperature on dynamics of sensory complexes in Escherichia coli chemotaxis. BMC Microbiol 2011; 11:222. [PMID: 21978288 PMCID: PMC3203854 DOI: 10.1186/1471-2180-11-222] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Accepted: 10/06/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Extracellular stimuli in chemotaxis of Escherichia coli and other bacteria are processed by large clusters of sensory complexes. The stable core of these clusters is formed by transmembrane receptors, a kinase CheA, and an adaptor CheW, whereas adaptation enzymes CheR and CheB dynamically associate with the clusters via interactions with receptors and/or CheA. Several biochemical studies have indicated the dependence of the sensory complex stability on the adaptive modification state of receptors and/or on temperature, which may potentially allow environment-dependent tuning of its signalling properties. However, the extent of such regulation in vivo and its significance for chemotaxis remained unclear. RESULTS Here we used fluorescence recovery after photobleaching (FRAP) to confirm in vivo that the exchange of CheA and CheW shows a modest dependency on the level of receptor modification/activity. An even more dramatic effect was observed for the exchange kinetics of CheR and CheB, indicating that their association with clusters may depend on the ability to bind substrate sites on receptors and on the regulatory phosphorylation of CheB. In contrast, environmental temperature did not have a discernible effect on stability of the cluster core. Strain-specific loss of E. coli chemotaxis at high temperature could instead be explained by a heat-induced reduction in the chemotaxis protein levels. Nevertheless, high basal levels of chemotaxis and flagellar proteins in common wild type strains MG1655 and W3110 enabled these strains to maintain their chemotactic ability up to 42°C. CONCLUSIONS Our results confirmed that clusters formed by less modified receptors are more dynamic, which can explain the previously observed adjustment of the chemotaxis response sensitivity according to the level of background stimulation. We further propose that the dependency of CheR exchange on the availability of unmethylated sites on receptors is important to improve the overall chemotaxis efficiency by suppressing molecular noise under conditions of high ligand concentrations. Moreover, the observed stability of the cluster core at high temperature is in line with the overall thermal robustness of the chemotaxis pathway and allows maintenance of chemotaxis up to 42°C in the common wild type strains of E. coli.
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Affiliation(s)
- Sonja Schulmeister
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
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Kentner D, Sourjik V. Use of Fluorescence Microscopy to Study Intracellular Signaling in Bacteria. Annu Rev Microbiol 2010; 64:373-90. [DOI: 10.1146/annurev.micro.112408.134205] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- David Kentner
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, D-69120 Heidelberg, Germany;
| | - Victor Sourjik
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, D-69120 Heidelberg, Germany;
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10
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Spatial organization in bacterial chemotaxis. EMBO J 2010; 29:2724-33. [PMID: 20717142 DOI: 10.1038/emboj.2010.178] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2010] [Accepted: 07/07/2010] [Indexed: 11/09/2022] Open
Abstract
Spatial organization of signalling is not an exclusive property of eukaryotic cells. Despite the fact that bacterial signalling pathways are generally simpler than those in eukaryotes, there are several well-documented examples of higher-order intracellular signalling structures in bacteria. One of the most prominent and best-characterized structures is formed by proteins that control bacterial chemotaxis. Signals in chemotaxis are processed by ordered arrays, or clusters, of receptors and associated proteins, which amplify and integrate chemotactic stimuli in a highly cooperative manner. Receptor clusters further serve to scaffold protein interactions, enhancing the efficiency and specificity of the pathway reactions and preventing the formation of signalling gradients through the cell body. Moreover, clustering can also ensure spatial separation of multiple chemotaxis systems in one bacterium. Assembly of receptor clusters appears to be a stochastic process, but bacteria evolved mechanisms to ensure optimal cluster distribution along the cell body for partitioning to daughter cells at division.
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Abstract
Myxococcus xanthus is a common soil bacterium with an intricate multicellular lifestyle that continues to challenge the way in which we conceptualize the capabilities of prokaryotic organisms. Myxococcus xanthus is the preferred laboratory representative from the Myxobacteria, a family of organisms distinguished by their ability to form highly structured biofilms that include tentacle-like packs of surface-gliding cell groups, synchronized rippling waves of oscillating cells and massive spore-filled aggregates that protrude upwards from the substratum to form fruiting bodies. But most of the Myxobacteria are also predators that thrive on the degradation of macromolecules released through the lysis of other microbial cells. The aim of this review is to examine our understanding of the predatory life cycle of M. xanthus. We will examine the multicellular structures formed during contact with prey, and the molecular mechanisms utilized by M. xanthus to detect and destroy prey cells. We will also examine our understanding of microbial predator-prey relationships and the prospects for how bacterial predation mechanisms can be exploited to generate new antimicrobial technologies.
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Affiliation(s)
- James E Berleman
- Department of Microbiology, The University of Iowa, Iowa City, IA 52242, USA
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12
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Kentner D, Sourjik V. Dynamic map of protein interactions in the Escherichia coli chemotaxis pathway. Mol Syst Biol 2009; 5:238. [PMID: 19156130 PMCID: PMC2644175 DOI: 10.1038/msb.2008.77] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2008] [Accepted: 12/17/2008] [Indexed: 11/10/2022] Open
Abstract
Protein-protein interactions play key roles in virtually all cellular processes, often forming complex regulatory networks. A powerful tool to study interactions in vivo is fluorescence resonance energy transfer (FRET), which is based on the distance-dependent energy transfer from an excited donor to an acceptor fluorophore. Here, we used FRET to systematically map all protein interactions in the chemotaxis signaling pathway in Escherichia coli, one of the most studied models of signal transduction, and to determine stimulation-induced changes in the pathway. Our FRET analysis identified 19 positive FRET pairs out of the 28 possible protein combinations, with 9 pairs being responsive to chemotactic stimulation. Six stimulation-dependent and five stimulation-independent interactions were direct, whereas other interactions were apparently mediated by scaffolding proteins. Characterization of stimulation-induced responses revealed an additional regulation through activity dependence of interactions involving the adaptation enzyme CheB, and showed complex rearrangement of chemosensory receptors. Our study illustrates how FRET can be efficiently employed to study dynamic protein networks in vivo.
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Affiliation(s)
- David Kentner
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Heidelberg, Germany
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13
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Sciara MI, Spagnuolo C, Jares-Erijman E, García Véscovi E. Cytolocalization of the PhoP response regulator in Salmonella enterica: modulation by extracellular Mg2+ and by the SCV environment. Mol Microbiol 2008; 70:479-93. [PMID: 18761685 DOI: 10.1111/j.1365-2958.2008.06427.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The PhoP/PhoQ two-component system plays an essential role regulating numerous virulence phenotypes in Salmonella enterica. Previous work showed that PhoQ, the sensor protein, switches between the kinase- and the phosphatase-dominant state in response to environmental Mg2+ availability. This switch defines the PhoP phosphorylation status and, as a result, the transcriptional activity of this regulator. In this work, using the FlAsH labelling technique, we examine PhoP cytolocalization in response to extracellular Mg2+ limitation in vitro and to the Salmonella-containing vacuole (SCV) environment in macrophage cells. We demonstrate that in these PhoP/PhoQ-inducing environments PhoP displays preferential localization to one cell pole, while being homogeneously distributed in the bacterial cytoplasm in repressing conditions. Polar localization is lost in the absence of PhoQ or when a non-phosphorylatable PhoP(D52A) mutant is expressed. However, when PhoP transcriptional activation is achieved in a Mg2+- and PhoQ-independent manner, PhoP regains asymmetric polar localization. In addition, we show that, in the analysed conditions, PhoQ cellular distribution does not parallel PhoP location pattern. These findings reveal that PhoP cellular location is dynamic and conditioned by its environmentally defined transcriptional status, showing a new insight in the PhoP/PhoQ system mechanism.
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Affiliation(s)
- Mariela I Sciara
- Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, S2002LRK Rosario, Argentina
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14
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Ping L, Weiner B, Kleckner N. Tsr-GFP accumulates linearly with time at cell poles, and can be used to differentiate 'old' versus 'new' poles, in Escherichia coli. Mol Microbiol 2008; 69:1427-38. [PMID: 18647166 DOI: 10.1111/j.1365-2958.2008.06372.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
SUMMARY In Escherichia coli, the chemotaxis receptor protein Tsr localizes abundantly to cell poles. The current study, utilizing a Tsr-GFP fusion protein and time-lapse fluorescence microscopy of individual cell lineages, demonstrates that Tsr accumulates approximately linearly with time at the cell poles and that, in consequence, more Tsr is present at the old pole of each cell than at its newborn pole. The rate of pole-localized Tsr accumulation is large enough that old and new poles can always be reliably distinguished, even for cells whose old poles have had only one generation to accumulate signal. Correspondingly, Tsr-GFP can be reliably used to assign new and old poles to any cell without use of information regarding pole heritage, thus providing a useful tool to analyse cells whose prior history is not available. The absolute level of Tsr-GFP at the old pole of a cell also provides a rough estimate of pole (and thus cell) age.
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Affiliation(s)
- Liyan Ping
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
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15
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Abstract
Chemoreceptors and cytoplasmic chemotaxis proteins in Escherichia coli form clusters that play a key role in signal processing. These clusters localize at cell poles and at specific positions along the cell body which correspond to future division sites, but the details of cluster formation and the mechanism of cluster distribution remain unclear. Here, we used fluorescence microscopy to investigate how the numbers and sizes of receptor clusters depend on the expression level of chemotaxis proteins and on the cell length. We show that the average cluster number saturates at high levels of protein expression at approximately 3.7 clusters per cell, well below the number of available positioning sites. Correspondingly, distances between clusters in filamentous cells saturate at an average of 1 mum but, even at saturating expression levels, individual cluster numbers and distances show a broad distribution around the mean. Our data imply a stochastic mode of cluster assembly, where a defined average interval between clusters along the cell body arises from competition between nucleation of new clusters and growth of existing clusters. Upon subsequent anchorage to defined lateral sites, clusters grow with rates that inversely depend on their size, and become polar upon several rounds of cell division.
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Affiliation(s)
- Sebastian Thiem
- Zentrum für Molekulare Biologie der Universität Heidelberg, Im Neuenheimer Feld 282, D-69120 Heidelberg, Germany
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16
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Thiem S, Kentner D, Sourjik V. Positioning of chemosensory clusters in E. coli and its relation to cell division. EMBO J 2007; 26:1615-23. [PMID: 17332753 PMCID: PMC1829377 DOI: 10.1038/sj.emboj.7601610] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2006] [Accepted: 01/25/2007] [Indexed: 11/09/2022] Open
Abstract
Chemotaxis receptors and associated signalling proteins in Escherichia coli form clusters that consist of thousands of molecules and are the largest native protein complexes described to date in bacteria. Clusters are located at the cell poles and laterally along the cell body, and play an important role in signal transduction. Much work has been done to study the structure and function of receptor clusters, but the significance of their positioning and the underlying mechanisms are not understood. Here, we used fluorescence imaging to study cluster distribution and follow cluster dynamics during cell growth. Our data show that lateral clusters localise to specific periodic positions along the cell body, which mark future division sites and are involved in the localisation of the replication machinery. The chemoreceptor cluster positioning is thus intricately related to the overall structure and division of an E. coli cell.
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Affiliation(s)
- Sebastian Thiem
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Heidelberg, Germany
| | - David Kentner
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Heidelberg, Germany
| | - Victor Sourjik
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Heidelberg, Germany
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Im Neuenheimer Feld 282, Heidelberg 69120, Germany. Tel.: +49 6221 546858; Fax: +49 6221 545894; E-mail:
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17
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Sourjik V, Vaknin A, Shimizu TS, Berg HC. In vivo measurement by FRET of pathway activity in bacterial chemotaxis. Methods Enzymol 2007; 423:365-91. [PMID: 17609141 DOI: 10.1016/s0076-6879(07)23017-4] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The two-component pathway in Escherichia coli chemotaxis has become a paradigm for bacterial signal processing. Genetics and biochemistry of the pathway as well as physiological responses have been studied in detail. Despite its relative simplicity, the chemotaxis pathway is renowned for its ability to amplify and integrate weak signals and for its robustness against various kinds of perturbations. All this information inspired multiple attempts at mathematical analysis and computer modeling, but a quantitative understanding of the pathway was hampered by our inability to follow the signal processing in vivo. To address this problem, we developed assays based on fluorescence resonance energy transfer (FRET) and bioluminescence resonance energy transfer (BRET) that enabled us to monitor activity-dependent protein interactions in real time directly in living cells. Here, we describe quantitative applications of these assays in cell populations and on a single-cell level to study the interaction of the phosphorylated response regulator CheY with its phosphatase CheZ. Since this interaction defines the rate of CheY dephosphorylation, which at steady state equals the rate of CheY phosphorylation, it can be used to characterize intracellular kinase activity and thus to analyze properties of the chemotaxis signaling network.
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Affiliation(s)
- Victor Sourjik
- ZMBH (Center for Molecular Biology Heidelberg), University of Heidelberg, Heidelberg, Germany
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18
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Perez E, Stock AM. Characterization of the Thermotoga maritima chemotaxis methylation system that lacks pentapeptide-dependent methyltransferase CheR:MCP tethering. Mol Microbiol 2006; 63:363-78. [PMID: 17163981 PMCID: PMC3645907 DOI: 10.1111/j.1365-2958.2006.05518.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Sensory adaptation in bacterial chemotaxis is mediated by covalent modifications of specific glutamate and glutamine residues within the cytoplasmic domains of methyl-accepting chemotaxis proteins (MCPs). In Escherichia coli and Salmonella enterica, efficient methylation of MCPs depends on the localization of methyltransferase CheR to MCP clusters through an interaction between the CheR beta-subdomain and a pentapeptide sequence (NWETF or NWESF) at the C-terminus of the MCP. In vitro methylation analyses utilizing S. enterica and Thermotoga maritima CheR proteins and MCPs indicate that MCP methylation in T. maritima occurs independently of a pentapeptide-binding motif. Kinetic and binding measurements demonstrate that despite efficient methylation, the interaction between T. maritima CheR and T. maritima MCPs is of relatively low affinity. Comparative protein sequence analyses of CheR beta-subdomains from organisms having MCPs that contain and/or lack pentapeptide-binding motifs identified key similarities and differences in residue conservation, suggesting the existence of two distinct classes of CheR proteins: pentapeptide-dependent and pentapeptide-independent methyltransferases. Analysis of MCP C-terminal ends showed that only approximately 10% of MCPs contain a putative C-terminal binding motif, the majority of which are restricted to the different proteobacteria classes (alpha, beta, gamma, delta). These findings suggest that tethering of CheR to MCPs is a relatively recent event in evolution and that the pentapeptide-independent methylation system is more common than the well-characterized pentapeptide-dependent methylation system.
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Affiliation(s)
- Eduardo Perez
- Center for Advanced Biotechnology and Medicine, UMDNJ-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854
- Department of Biochemistry, UMDNJ-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854
| | - Ann M. Stock
- Center for Advanced Biotechnology and Medicine, UMDNJ-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854
- Department of Biochemistry, UMDNJ-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854
- Howard Hughes Medical Institute, UMDNJ-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854
- Corresponding Author: Mailing address: CABM, 679 Hoes Lane, Piscataway, NJ 08854-5627. Phone: (732) 235-4844. Fax: (732) 235-5289.
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Kentner D, Thiem S, Hildenbeutel M, Sourjik V. Determinants of chemoreceptor cluster formation in Escherichia coli. Mol Microbiol 2006; 61:407-17. [PMID: 16856941 DOI: 10.1111/j.1365-2958.2006.05250.x] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Chemotactic stimuli in bacteria are sensed by large sensory complexes, or receptor clusters, that consist of tens of thousands of proteins. Receptor clusters appear to play a key role in signal processing, but their structure remains poorly understood. Here we used fluorescent protein fusions to study in vivo formation of the cluster core, which consists of receptors, a kinase CheA and an assisting protein CheW. We show that receptors aggregate through their cytoplasmic domains even in the absence of other chemotaxis proteins. Clustering is further enhanced by the binding of CheW. Surprisingly, we observed that some fragments of CheA bind receptor clusters well in the absence of CheW, although the latter does assist the binding of full-length CheA. The resulting mode of receptor cluster formation is consistent with an experimentally observed flexible stoichiometry of chemosensory complexes and with assumptions of recently proposed computer models of signal processing in chemotaxis.
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Affiliation(s)
- David Kentner
- Zentrum für Molekulare Biologie der Universität Heidelberg, Im Neuenheimer Feld 282, D-69120 Heidelberg, Germany
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20
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Güvener ZT, Tifrea DF, Harwood CS. Two different Pseudomonas aeruginosa chemosensory signal transduction complexes localize to cell poles and form and remould in stationary phase. Mol Microbiol 2006; 61:106-18. [PMID: 16824098 DOI: 10.1111/j.1365-2958.2006.05218.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Pseudomonas aeruginosa has sets of sensory genes designated che and che2. The che genes are required for flagella-mediated chemotaxis. The che2 genes are expressed in the stationary phase of growth and are probably also involved in flagella-mediated behavioural responses. P. aeruginosa also has 26 chemoreceptor genes, six of which are preferentially expressed in stationary phase. Subcellular localization experiments indicated that Che proteins form signal transduction complexes at cell poles throughout growth. Cyan fluorescent protein (CFP)-tagged McpA, a stationary phase-expressed chemoreceptor, appeared and colocalized with yellow fluorescent protein (YFP)-tagged CheA when cells entered stationary phase. This indicates that P. aeruginosa chemotaxis protein complexes are subject to remoulding by chemoreceptor proteins that are expressed when cells stop growing. CheA-CFP and CheY2-YFP tagged proteins that were coexpressed in the same cell had separate subcellular locations, indicating that Che2 proteins do not enter into direct physical interactions with Che proteins. Che2 protein complex formation required McpB, another stationary phase induced chemoreceptor that is predicted to be soluble. This implies that Che2 complexes have a function that depends on just one chemoreceptor. Our results suggest that motile P. aeruginosa cells have signal transduction systems that are adapted to allow non-growing cells to sense and respond to their environment differently from actively growing cells.
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Affiliation(s)
- Zehra Tüzün Güvener
- Department of Microbiology, University of Washington, Seattle, WA 98195, USA
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Shiomi D, Yoshimoto M, Homma M, Kawagishi I. Helical distribution of the bacterial chemoreceptor via colocalization with the Sec protein translocation machinery. Mol Microbiol 2006; 60:894-906. [PMID: 16677301 PMCID: PMC1513513 DOI: 10.1111/j.1365-2958.2006.05145.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
In Escherichia coli, chemoreceptor clustering at a cell pole seems critical for signal amplification and adaptation. However, little is known about the mechanism of localization itself. Here we examined whether the aspartate chemoreceptor (Tar) is inserted directly into the polar membrane by using its fusion to green fluorescent protein (GFP). After induction of Tar–GFP, fluorescent spots first appeared in lateral membrane regions, and later cell poles became predominantly fluorescent. Unexpectedly, Tar–GFP showed a helical arrangement in lateral regions, which was more apparent when a Tar–GFP derivative with two cysteine residues in the periplasmic domain was cross-linked to form higher oligomers. Moreover, similar distribution was observed even when the cytoplasmic domain of the double cysteine Tar–GFP mutant was replaced by that of the kinase EnvZ, which does not localize to a pole. Observation of GFP–SecE and a translocation-defective MalE–GFP mutant, as well as indirect immunofluorescence microscopy on SecG, suggested that the general protein translocation machinery (Sec) itself is arranged into a helical array, with which Tar is transiently associated. The Sec coil appeared distinct from the MreB coil, an actin-like cytoskeleton. These findings will shed new light on the mechanisms underlying spatial organization of membrane proteins in E. coli.
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Affiliation(s)
- Daisuke Shiomi
- Division of Biological Science, Graduate School of Science, Nagoya UniversityChikusa-ku, Nagoya 464-8602, Japan
| | - Masayuki Yoshimoto
- Division of Biological Science, Graduate School of Science, Nagoya UniversityChikusa-ku, Nagoya 464-8602, Japan
| | - Michio Homma
- Division of Biological Science, Graduate School of Science, Nagoya UniversityChikusa-ku, Nagoya 464-8602, Japan
| | - Ikuro Kawagishi
- Division of Biological Science, Graduate School of Science, Nagoya UniversityChikusa-ku, Nagoya 464-8602, Japan
- Institute for Advanced Research, Nagoya UniversityChikusa-ku, Nagoya 464-8602, Japan
- For correspondence. E-mail ; Tel. (+81) 52 789 2993; Fax (+81) 52 789 3001
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22
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Baker MD, Wolanin PM, Stock JB. Systems biology of bacterial chemotaxis. Curr Opin Microbiol 2006; 9:187-92. [PMID: 16529985 DOI: 10.1016/j.mib.2006.02.007] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2005] [Accepted: 02/24/2006] [Indexed: 11/24/2022]
Abstract
Motile bacteria regulate chemotaxis through a highly conserved chemosensory signal-transduction system. System-wide analyses and mathematical modeling are facilitated by extensive experimental observations regarding bacterial chemotaxis proteins, including biochemical parameters, protein structures and protein-protein interaction maps. Thousands of signaling and regulatory chemotaxis proteins within a bacteria cell form a highly interconnected network through distinct protein-protein interactions. A bacterial cell is able to respond to multiple stimuli through a collection of chemoreceptors with different sensory modalities, which interact to affect the cooperativity and sensitivity of the chemotaxis response. The robustness or insensitivity of the chemotaxis system to perturbations in biochemical parameters is a product of the system's hierarchical network architecture.
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Affiliation(s)
- Melinda D Baker
- Princeton University, Department of Molecular Biology, Lewis Thomas Laboratory, Princeton, NJ 08544, USA
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Shiomi D, Banno S, Homma M, Kawagishi I. Stabilization of polar localization of a chemoreceptor via its covalent modifications and its communication with a different chemoreceptor. J Bacteriol 2005; 187:7647-54. [PMID: 16267289 PMCID: PMC1280290 DOI: 10.1128/jb.187.22.7647-7654.2005] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In the chemotaxis of Escherichia coli, polar clustering of the chemoreceptors, the histidine kinase CheA, and the adaptor protein CheW is thought to be involved in signal amplification and adaptation. However, the mechanism that leads to the polar localization of the receptor is still largely unknown. In this study, we examined the effect of receptor covalent modification on the polar localization of the aspartate chemoreceptor Tar fused to green fluorescent protein (GFP). Amidation (and presumably methylation) of Tar-GFP enhanced its own polar localization, although the effect was small. The slight but significant effect of amidation on receptor localization was reinforced by the fact that localization of a noncatalytic mutant version of GFP-CheR that targets to the C-terminal pentapeptide sequence of Tar was similarly facilitated by receptor amidation. Polar localization of the demethylated version of Tar-GFP was also enhanced by increasing levels of the serine chemoreceptor Tsr. The effect of covalent modification on receptor localization by itself may be too small to account for chemotactic adaptation, but receptor modification is suggested to contribute to the molecular assembly of the chemoreceptor/histidine kinase array at a cell pole, presumably by stabilizing the receptor dimer-to-dimer interaction.
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Affiliation(s)
- Daisuke Shiomi
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Japan
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24
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Abstract
The site of cell division in bacterial cells is placed with high fidelity at a designated position, usually the midpoint of the cell. In normal cell division in Escherichia coli this is accomplished by the action of the Min proteins, which maintain a high concentration of a septation inhibitor near the ends of the cell, and a low concentration at midcell. This leaves the midcell site as the only available location for formation of the division septum. In other species, such as Bacillus subtilis, this general paradigm is maintained, although some of the proteins differ and the mechanisms used to localize the proteins vary. A second mechanism of negative regulation, the nucleoid-occlusion system, prevents septa forming over nucleoids. This system functions in Gram-negative and Gram-positive bacteria, and is especially important in cells that lack the Min system or in cells in which nucleoid replication or segregation are defective. Here, we review the latest findings on these two systems.
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Affiliation(s)
- Lawrence Rothfield
- Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, Farmington, Connecticut 06030, USA.
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Lybarger SR, Nair U, Lilly AA, Hazelbauer GL, Maddock JR. Clustering requires modified methyl-accepting sites in low-abundance but not high-abundance chemoreceptors of Escherichia coli. Mol Microbiol 2005; 56:1078-86. [PMID: 15853891 DOI: 10.1111/j.1365-2958.2005.04593.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Chemotaxis signalling complexes of Escherichia coli, composed of chemoreceptors, CheA and CheW, form clusters located predominantly at cell poles. As the only kind of receptor in a cell, high-abundance receptors are polar and clustered whereas low-abundance chemoreceptors are polar but largely unclustered. We found that clustering was a function of the cytoplasmic, carboxyl-terminal domain and that effective clustering was conferred on low-abundance receptors by addition of the approximately 20-residue sequence from the carboxyl terminus of either high-abundance receptor. These sequences are different but share a carboxyl-terminal pentapeptide that enhances adaptational covalent modification and allows a physiological balance between modified and unmodified methyl-accepting sites, implying that receptor modification might influence clustering. Thus we investigated directly effects of modification state on chemoreceptor clustering. As the sole receptor type in a cell, low-abundance receptors were clustered only if modified, but high-abundance receptors were clustered independent of extent of modification. This difference could mean that the two receptor types are fundamentally different or that they are poised at different positions in the same conformational equilibrium. Notably, no receptor perturbation we tested altered a predominant location at cell poles, emphasizing a distinction between determinants of clustering and polar localization.
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Affiliation(s)
- Suzanne R Lybarger
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, 830 North University, Ann Arbor, MI 48109, USA
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Fukuoka H, Yakushi T, Kusumoto A, Homma M. Assembly of motor proteins, PomA and PomB, in the Na+-driven stator of the flagellar motor. J Mol Biol 2005; 351:707-17. [PMID: 16038931 DOI: 10.1016/j.jmb.2005.06.037] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2005] [Revised: 06/13/2005] [Accepted: 06/15/2005] [Indexed: 11/18/2022]
Abstract
PomA and PomB are transmembrane proteins that form the stator complex in the sodium-driven flagellar motor of Vibrio alginolyticus and are believed to surround the rotor part of the flagellar motor. We constructed and observed green fluorescent protein (GFP) fusions of the stator proteins PomA and PomB in living cells to clarify how stator proteins are assembled and installed into the flagellar motor. We were able to demonstrate that GFP-PomA and GFP-PomB localized to a cell pole dependent on the presence of the polar flagellum. Localization of the GFP-fused stator proteins required their partner subunit, PomA or PomB, and the C-terminal domain of PomB, which has a peptidoglycan-binding motif. Each of the GFP-fused stator proteins was co-isolated with its partner subunit from detergent-solubilized membrane. From these lines of evidence, we have demonstrated that the stator proteins are incorporated into the flagellar motor as a PomA/PomB complex and are fixed to the cell wall via the C-terminal domain of PomB.
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Affiliation(s)
- Hajime Fukuoka
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-Ku, Nagoya 464-8602, Japan
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Coleman MD, Bass RB, Mehan RS, Falke JJ. Conserved glycine residues in the cytoplasmic domain of the aspartate receptor play essential roles in kinase coupling and on-off switching. Biochemistry 2005; 44:7687-95. [PMID: 15909983 PMCID: PMC2895725 DOI: 10.1021/bi0501479] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The aspartate receptor of the bacterial chemotaxis pathway serves as a scaffold for the formation of a multiprotein signaling complex containing the receptor and the cytoplasmic pathway components. Within this complex, the receptor regulates the autophosphorylation activity of histidine kinase CheA, thereby controlling the signals sent to the flagellar motor and the receptor adaptation system. The receptor cytoplasmic domain, which controls the on-off switching of CheA, possesses 14 glycine residues that are highly conserved in related receptors. In principle, these conserved glycines could be required for static turns, bends, or close packing in the cytoplasmic domain, or they could be required for conformational dynamics during receptor on-off switching. To determine which glycines are essential and to probe their functional roles, we have substituted each conserved glycine with both alanine and cysteine, and then measured the effects on receptor function in vivo and in vitro. The results reveal a subset of six glycines which are required for receptor function during cellular chemotaxis. Two of these essential glycines (G388 and G391) are located at a hairpin turn at the distal end of the folded cytoplasmic domain, where they are required for the tertiary fold of the signaling subdomain and for CheA kinase activation. Three other essential glycines (G338, G339, and G437) are located at the border between the adaptation and signaling subdomains, where they play key roles in CheA kinase activation and on-off switching. These three glycines form a ring around the four-helix bundle that comprises the receptor cytoplasmic domain, yielding a novel architectural feature termed a bundle hinge. The final essential glycine (G455) is located in the adaptation subdomain where it is required for on-off switching. Overall, the findings confirm that six of the 14 conserved cytoplasmic glycines are essential for receptor function because they enable helix turns and bends required for native receptor structure, and in some cases for switching between the on and off signaling states. An initial working model proposes that the novel bundle hinge enables the four-helix bundle to bend, perhaps during the assembly of the receptor trimer of dimers or during on-off switching. More generally, the findings predict that certain human disease states, including specific cancers, could be triggered by lock-on mutations at essential glycine positions that control the on-off switching of receptors and signaling proteins.
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Affiliation(s)
| | | | | | - Joseph J. Falke
- To whom correspondence should be addressed. . Telephone: (303) 492-3503. Fax: (303) 492-5894
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Drew DA, Osborn MJ, Rothfield LI. A polymerization-depolymerization model that accurately generates the self-sustained oscillatory system involved in bacterial division site placement. Proc Natl Acad Sci U S A 2005; 102:6114-8. [PMID: 15840714 PMCID: PMC1087953 DOI: 10.1073/pnas.0502037102] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Determination of the proper site for division in Escherichia coli and other bacteria involves a unique spatial oscillatory system in which membrane-associated structures composed of the MinC, MinD and MinE proteins oscillate rapidly between the two cell poles. In vitro evidence indicates that this involves ordered cycles of assembly and disassembly of MinD polymers. We propose a mathematical model to explain this behavior. Unlike previous attempts, the present approach is based on the expected behavior of polymerization-depolymerization systems and incorporates current knowledge of the biochemical properties of MinD and MinE. Simulations based on the model reproduce all of the known topological and temporal characteristics of the in vivo oscillatory system.
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Affiliation(s)
- Donald A Drew
- Department of Mathematical Sciences, Rensselaer Polytechnic Institute, Troy, NY 12180-3590, USA
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Abstract
Chemotaxis in Escherichia coli is one of the most thoroughly studied model systems for signal transduction. Receptor-kinase complexes, organized in clusters at the cell poles, sense chemoeffector stimuli and transmit signals to flagellar motors by phosphorylation of a diffusible response regulator protein. Despite the apparent simplicity of the signal transduction pathway, the high sensitivity, wide dynamic range and integration of multiple stimuli of this pathway remain unexplained. Recent advances in computer modeling and in quantitative experimental analysis suggest that cooperative protein interactions in receptor clusters play a crucial role in the signal processing during bacterial chemotaxis.
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Affiliation(s)
- Victor Sourjik
- ZMBH, University of Heidelberg, Im Neuenheimer Feld 282, D-69120 Heidelberg, Germany.
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