Covalent Modification Regulates Ligand Binding to Receptor Complexes in the Chemosensory System of Escherichia coli

Li, Guoyong; Weis, Robert M.

doi:10.1016/s0092-8674(00)80671-6

Cited by 183 publications

(254 citation statements)

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“…In addition, receptors are coupled to one another. For instance, the response to attractant stimulation is cooperative; Hill coefficients as high as 10 have been observed [11,12]. Strikingly, the presence of heterologous receptors or homologous receptors in different states of adaptational modification alters cooperativity and/or sensitivity to stimulation, as well as the level of kinase activation [11][12][13][14].…”

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confidence: 99%

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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confidence: 99%

Bacterial chemoreceptors: high-performance signaling in networked arrays

Hazelbauer

Falke

Parkinson

2008

Trends in Biochemical Sciences

588

804

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“…The other soluble components of the chemotaxis pathway, CheY and CheZ, bind to receptor-associated CheA; thus, all of the pathway components are organized in a single supermolecular signaling complex. In living cells, the trimeric signaling complexes are localized to the cell poles, where they form limited higher-order associations (5,(10)(11)(12)(13)(14).…”

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confidence: 99%

Adaptation Mechanism of the Aspartate Receptor: Electrostatics of the Adaptation Subdomain Play a Key Role in Modulating Kinase Activity

2005

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The aspartate receptor of the Escherichia coli and Salmonella typhimurium chemotaxis pathway generates a transmembrane signal that regulates the activity of the cytoplasmic kinase CheA. Previous studies have identified a region of the cytoplasmic domain that is critical to receptor adaptation and kinase regulation. This region, termed the adaptation subdomain, contains a high density of acidic residues, including specific glutamate residues that serve as receptor adaptation sites. However, the mechanism of signal propagation through this region remains poorly understood. This study uses site-directed mutagenesis to neutralize each acidic residue within the subdomain to probe the hypothesis that electrostatics in this region play a significant role in the mechanism of kinase activation and modulation. Each point mutant was tested for its ability to regulate chemotaxis in vivo and kinase activity in vitro. Four point mutants (D273N, E281Q, D288N, and E477Q) were found to superactivate the kinase relative to the wild-type receptor, and all four of these kinaseactivating substitutions are located along the same intersubunit interface as the adaptation sites. These activating substitutions retained the wild-type ability of the attractant-occupied receptor to inhibit kinase activity. When combined in a quadruple mutant (D273N/E281Q/D288N/E477Q), the four charge-neutralizing substitutions locked the receptor in a kinase-superactivating state that could not be fully inactivated by the attractant. Similar lock-on character was observed for a charge reversal substitution, D273R. Together, these results implicate the electrostatic interactions at the intersubunit interface as a major player in signal transduction and kinase regulation. The negative charge in this region destabilizes the local structure in a way that enhances conformational dynamics, as detected by disulfide trapping, and this effect is reversed by charge neutralization of the adaptation sites. Finally, two substitutions (E308Q and E463Q) preserved normal kinase activation in vitro but blocked cellular chemotaxis in vivo, suggesting that these sites lie within the docking site of an adaptation enzyme, CheR or CheB. Overall, this study highlights the importance of electrostatics in signal transduction and regulation of kinase activity by the cytoplasmic domain of the aspartate receptor.The aspartate receptor of bacterial chemotaxis is one of the best-characterized members of a large family of cell surface receptors that modulate two-component signaling pathways (reviewed in refs 1-6). Through regulation of the associated histidine kinase CheA, the aspartate receptor controls cellular chemotaxis in response to changing concentrations of the chemoattractant aspartate, allowing the cell to move up an attractant concentration gradient. The receptor is an oligomer composed of three homodimers that assemble to form a trimer of dimers, as illustrated in Figure 1A. The chemotaxis signaling pathway is triggered by aspartate † Support provided by NIH Grant GM ...

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“…Complexes of Tar or Tsr, CheA, and CheW have also been formed from purified components in vitro (20,21). The complexes are characterized by Ͼ100-fold increases in CheA-kinase activity that are subject to inhibition by addition of aspartate or serine (22,23).…”

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Self-assembly of receptor/signaling complexes in bacterial chemotaxis

Wolanin¹,

Baker

Francis³

et al. 2006

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

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Escherichia coli chemotaxis is mediated by membrane receptor͞ histidine kinase signaling complexes. Fusing the cytoplasmic domain of the aspartate receptor, Tar, to a leucine zipper dimerization domain produces a hybrid, lzTar C, that forms soluble complexes with CheA and CheW. The three-dimensional reconstruction of these complexes was different from that anticipated based solely on structures of the isolated components. We found that analogous complexes self-assembled with a monomeric cytoplasmic domain fragment of the serine receptor without the leucine zipper dimerization domain. These complexes have essentially the same size, composition, and architecture as those formed from lzTar C. Thus, the organization of these receptor͞signaling complexes is determined by conserved interactions between the constituent chemotaxis proteins and may represent the active form in vivo. To understand this structure in its cellular context, we propose a model involving parallel membrane segments in receptor-mediated CheA activation in vivo.CheA ͉ histidine kinase ͉ serine receptor ͉ signal transduction

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Covalent Modification Regulates Ligand Binding to Receptor Complexes in the Chemosensory System of Escherichia coli

Cited by 183 publications

References 42 publications

Bacterial chemoreceptors: high-performance signaling in networked arrays

Bacterial chemoreceptors: high-performance signaling in networked arrays

Adaptation Mechanism of the Aspartate Receptor: Electrostatics of the Adaptation Subdomain Play a Key Role in Modulating Kinase Activity

Self-assembly of receptor/signaling complexes in bacterial chemotaxis

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