Electron Microscopic Analysis of Membrane Assemblies Formed by the Bacterial Chemotaxis Receptor Tsr

Weis, Robert M.; Hirai, Takeshi; Chalah, Anas; Kessel, Martin; Peters, Peter J.; Subramaniam, Sriram

doi:10.1128/jb.185.12.3636-3643.2003

Cited by 63 publications

(95 citation statements)

References 47 publications

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“…The sequence locations, and the exposed and buried faces of these helices, are the same as identified previously by cysteine-scanning of an intact chemoreceptor [44], and the length of the domain is close to that deduced by analysis with electron microscopy [41]. Thus, at least in one signaling state, the chemoreceptor signal-conversion module might resemble the HAMP NMR structure, which could connect to adjoining receptor modules through extensions of its helical segments.…”

Section: Chemoreceptor Homodimers: Structuresupporting

confidence: 76%

“…Electron microscopy [41] reveals E. coli receptor dimers as ~300Å needle-like proteins oriented approximately normal to the membrane. The needle-like shape and dimensions imply that the helical receptor sub-domains for which detailed structural information is available are arranged end-toend (Box 3).…”

Section: Chemoreceptor Homodimers: Structurementioning

confidence: 99%

“…Modules are indicated on the left, roles or identities of module segments in the middle and notable features on the right. The model is based on the shape of an intact, membrane-embedded receptor revealed by electron microscopy [41], the X-ray structure of a periplasmic fragment [67], the X-ray structure of a cytoplasmic fragment [25], patterns of disulfide formation between introduced cysteines [49,57,68] and a model of the signal conversion module based on an NMR structure of a homologous HAMP domain [43].…”

Section: Figure Imentioning

confidence: 99%

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Bacterial chemoreceptors: high-performance signaling in networked arrays

Hazelbauer

Falke

Parkinson

2008

Trends in Biochemical Sciences

588

804

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Chemoreceptors are crucial components in the bacterial sensory systems that mediate chemotaxis. Chemotactic responses exhibit exquisite sensitivity, extensive dynamic range and precise adaptation. The mechanisms that mediate these high-performance functions involve not only actions of individual proteins but also interactions among clusters of components, localized in extensive patches of thousands of molecules. Recently, these patches have been imaged in native cells, important features of chemoreceptor structure and on-off switching have been identified, and new insights have been gained into the structural basis and functional consequences of higher order interactions among sensory components. These new data suggest multiple levels of molecular interactions, each of which contribute specific functional features and together create a sophisticated signaling device. High-performance signaling in bacterial chemotaxisThe high-performance chemotaxis signaling system of Escherichia coli (Box 1) involves a limited number of components but notable sophistication [1][2][3][4]. This system has become a paradigm for molecular characterization of biological signaling mechanisms. Transmembrane chemoreceptors, known as methyl-accepting chemotaxis proteins (MCPs), direct cell locomotion by regulating the histidine kinase CheA; CheA phosphorylates a response regulator, which in turn controls the rotational direction of the flagellar motor. Chemotactic sensitivity and the range of signal detection are regulated by adaptational modification of chemoreceptors via reversible glutamyl methylation. The resulting interplay between motor control and sensory adaptation produces directed motile behavior. E. coli chemoreceptors are the most extensively studied representatives of the MCP super-family, central components of homologous systems that mediate tactic responses [5,6] across the phylogenetic diversity of bacteria and archaea [7].In E. coli chemotaxis proteins cluster in membrane-associated patches [8]. Interaction within patches is thought to contribute to notable features of the signaling system: high sensitivity, wide dynamic range, extensive cooperativity and precise adaptation. Delineating the molecular mechanisms underlying these features will require knowledge of structures of the components, complexes and higher order arrays. In addition it will require definition of organization at the multiple levels of interaction among signaling components and an understanding of the changes in components and their interactions that mediate signaling at each level. In the past few years, notable progress has been made toward acquiring the NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript information and insights necessary for understanding these molecular mechanisms. This review describes that progress. Here we follow the lead of most investigators in the area, and do not distinguish between studies of first cousins E. coli and Salmonella enterica serovar Typhimurium. Thus, referenc...

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Section: Chemoreceptor Homodimers: Structuresupporting

confidence: 76%

Section: Chemoreceptor Homodimers: Structurementioning

confidence: 99%

Section: Figure Imentioning

confidence: 99%

See 1 more Smart Citation

Bacterial chemoreceptors: high-performance signaling in networked arrays

Hazelbauer

Falke

Parkinson

2008

Trends in Biochemical Sciences

588

804

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“…32 for a review). Extended arrays of receptors have been visualized by EM in cells overexpressing Tsr in the absence of CheW and CheA (34,35). In these cells, Tsr tended to form bilaminar structures where the signaling domains are apparently interdigitated in an antiparallel manner.…”

Section: Discussionmentioning

confidence: 99%

Three-dimensional structure and organization of a receptor/signaling complex

Francis

Wolanin

Stock

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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Transmembrane signaling in bacterial chemotaxis has become an important model system for experimental and theoretical studies. These studies have provided a wealth of detailed molecular structures, including the structures of CheA, CheW, and the cytoplasmic domain of the serine receptor Tsr. How these three proteins interact to form the receptor͞signaling complex remains unknown. By using EM and single-particle image analysis, we present a three-dimensional reconstruction of the receptor͞signaling complex. The complex contains CheA, CheW, and the cytoplasmic portion of the aspartate receptor Tar. We observe density consistent with a structure containing 24 aspartate-receptor monomers and additional density sufficient to house the expected four CheA monomers and six CheW monomers. Within this bipolar structure are four groups of three receptor dimers that are not threefold symmetric and are therefore unlike the symmetric trimers observed in the x-ray crystal structure of the cytoplasmic domain of the serine receptor. In the latter, the interdimer contacts occur in the signaling domains near the hairpin loop. In our structure, the signaling domains within trimers appear spaced apart by the presence of CheA and CheW. This structure argues against models where one CheA and one CheW bind to the outer face of each of the dimers in the trimer. This structure of the receptor͞signaling complex provides an additional basis for understanding the architecture of the large arrays of chemotaxis receptors, CheA, and CheW found at the cell poles in motile bacteria.chemotaxis ͉ electron microscopy ͉ macromolecular assembly ͉ signal transduction M otile bacteria are capable of detecting and moving in response to gradients of nutrients, oxygen, light, and other stimuli. They do so in response to temporal changes in the stimuli by altering the behavior of the motors that generate the force for cell movement. The signal transduction system controlling bacterial chemotaxis has become an important model for the study of transmembrane signaling, and the most studied system is that in Escherichia coli.The core components of the E. coli chemotaxis signaltransduction system are found in nearly all motile bacteria and consist of transmembrane chemoreceptors; an associated histidine kinase, CheA; and an associated CheA-activator, CheW. Signaling occurs within the context of the assembled receptor͞ CheW͞CheA complexes within a large, densely packed patch of chemoreceptors, which is typically located at one (or both) poles of the cell (1). No gross structural changes in the receptor͞ signaling complex are observed in response to stimulatory ligands (2).Recent studies and modeling of the chemotaxis system have emphasized the importance of interactions among large numbers of receptors in terms of the system's sensitivity and adaptive response (3, 4), and chemoreceptors for different ligands appear to communicate with one another (3). The lack of detailed information about how CheA and CheW interact with the chemoreceptors and each other in the ...

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“…Homodimers can form trimers by interactions at the distal tips of their cytoplasmic domains (4, 6). They can also form higher order complexes and extended arrays by themselves or in complex with CheA and CheW (5,7,8). The interactions that create chemoreceptor clusters have not been defined.…”

Section: Chemoreceptor Interactionsmentioning

confidence: 99%

Nanodiscs separate chemoreceptor oligomeric states and reveal their signaling properties

Boldog

Grimme

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

187

245

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Bacterial chemoreceptors are transmembrane homodimers that can form trimers, higher order arrays, and extended clusters as part of signaling complexes. Interactions of dimers in oligomers are thought to confer cooperativity and cross-receptor influences as well as a 35-fold gain between ligand binding and altered kinase activity. In addition, higher order interactions among dimers are necessary for the observed patterns of assistance in adaptational modification among different receptors. Elucidating mechanisms underlying these properties will require defining which receptor functions can be performed by dimers and which require specific higher order interactions. However, such an assignment has not been possible. Here, we used Nanodiscs, an emerging technology for manipulating membrane proteins, to prepare small particles of lipid bilayer containing one or only a few chemoreceptor dimers. We found that receptor dimers isolated in individual Nanodiscs were readily modified, bound ligand, and performed transmembrane signaling. However, they were hardly able to activate the chemotaxis histidine kinase. Instead, maximal activation and thus full-range control of kinase occurred preferentially in discs containing approximately three chemoreceptor dimers. The sharp dependence of kinase activation on this number of receptors per dimer implies that the core structural unit of kinase activation and control is a trimer of dimers. Thus, our observations demonstrate that chemoreceptor transmembrane signaling does not require oligomeric organization beyond homodimers and implicate a trimer of dimers as the unit of downstream signaling. membrane protein ͉ nanoparticle ͉ self-assembly ͉ transmembrane receptor ͉ transmembrane signaling M otile bacteria move to favorable chemical environments through chemotaxis. The phenomenon and its mechanisms have been extensively characterized in Escherichia coli and its relatives (1-3). Transmembrane chemoreceptors form signaling complexes with the autophosphorylating histidine kinase CheA and coupling protein CheW. Phospho-CheA mediates phosphorylation of response regulator CheY. Phospho-CheY binds to the flagellar rotary motor, causing rotational reversal, which creates tumbles that alter swimming direction. Formation of signaling complexes activates CheA autophosphorylation and places that activity under the control of chemoreceptors. The sensory system directs cells toward favorable environments by modulating kinase activity, thus controlling the probability of tumbles and resulting directional changes. Transmembrane SignalingTransmembrane signaling by chemoreceptors (3) couples binding of stimulant molecules by its periplasmic domain with changes in its cytoplasmic domain that alter activation of the kinase and change the propensity for covalent modification of that domain, specifically methylation and demethylation at several glutamyl residues (four to six, depending on the specific receptor). Methylation is catalyzed by methyltransferase CheR. Demethylation is catalyzed by methyleste...

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Electron Microscopic Analysis of Membrane Assemblies Formed by the Bacterial Chemotaxis Receptor Tsr

Cited by 63 publications

References 47 publications

Bacterial chemoreceptors: high-performance signaling in networked arrays

Bacterial chemoreceptors: high-performance signaling in networked arrays

Three-dimensional structure and organization of a receptor/signaling complex

Nanodiscs separate chemoreceptor oligomeric states and reveal their signaling properties

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