Chimeric chemosensory transducers of Escherichia coli.

Krikos, Alexandra; Conley, Matthew P.; Boyd, Alan; Berg, Howard C.; Simon, Melvin I.

doi:10.1073/pnas.82.5.1326

Cited by 135 publications

(125 citation statements)

References 31 publications

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“…These conserved regions are presumed to play ubiquitous roles in receptor adaptation and histidine kinase regulation. Indeed, functional chimaeric receptors have been generated by swapping the cytoplasmic domains of closely or distantly related MTP receptors, indicating that the cytoplasmic domain is a fully interchangeable signaling module [28][29][30][31]. Early circular dichroism, hydrodynamic and NMR studies of isolated MTPCDs have suggested that the domain structure is predominantly α-helical and highly elongated [32][33][34].…”

Section: Conserved Cytoplasmic Domain Of the Methyl-accepting Taxis Pmentioning

confidence: 99%

Structure of a conserved receptor domain that regulates kinase activity: the cytoplasmic domain of bacterial taxis receptors

Falke

Kim

2000

Current Opinion in Structural Biology

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Many bacteria are motile and use a conserved class of transmembrane sensory receptor to regulate cellular taxis toward an optimal living environment. These conserved receptors are typically stimulated by extracellular signals, but also undergo adaptation via covalent modification at specific sites on their cytoplasmic domains. The function of the cytoplasmic domain is to integrate the extracellular and adaptive signals, and to use this integrated information to regulate an associated histidine kinase. The kinase, in turn, triggers a cytoplasmic phosphorylation pathway of the twocomponent class. The high-resolution structure of a receptor cytoplasmic domain has recently been determined by crystallographic methods and is largely consistent with a structural model independently generated by chemical studies of the domain in the full-length, membrane-bound receptor. These results represent an important step toward a mechanistic understanding of receptorto-kinase information transfer.

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Section: Conserved Cytoplasmic Domain Of the Methyl-accepting Taxis Pmentioning

confidence: 99%

Structure of a conserved receptor domain that regulates kinase activity: the cytoplasmic domain of bacterial taxis receptors

Falke

Kim

2000

Current Opinion in Structural Biology

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“…Plasmids pAB157, pAB160, pTsar-Cla, and pTsar-Nde carrying the chimeric genes encoding Tasr-468, Tasr-256, Tsar-468, and Tsar-256, respectively, were provided by M. I. Simon of the California Institute of Technology (15). 3 Construction of Chimeric Chemoreceptor Genes-The pUC118-based plasmids, which encode the Tar-Tsr hybrids Tasr-502, Tasr-441, Tasr431, Tasr-375, and Tasr-309 (Tar residue numbering), were constructed by spontaneous homologous recombination between tar and tsr genes placed in tandem (23).…”

Section: Plasmid Pfh101mentioning

confidence: 99%

“…These receptors also sense changes in pH o (15). Moreover, the minor chemoreceptors Trg and Tap mediate Tar-and Tsr-type responses, respectively, to changes in pH i when they are expressed as the sole chemoreceptor (16).…”

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confidence: 99%

“…In fact, the activity of the histidine kinase CheA depends sharply on pH (14). However, the chemoreceptors have been considered to be the primary sensors for pH i , because the two major chemoreceptors, Tsr and Tar, have opposite pH i -sensing properties (15). When expressed as a sole chemoreceptor, Tsr mediates repellent and attractant responses to decreases and increases in pH i , respectively, whereas under these conditions Tar mediates the responses * This work was supported in part by grants-in-aid for scientific research from the Japan Society for the Promotion of Science (to T. U. and I. K.) and from the Takeda Science Foundation (to I. K.).…”

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confidence: 99%

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Sensing of Cytoplasmic pH by Bacterial Chemoreceptors Involves the Linker Region That Connects the Membrane-spanning and the Signal-modulating Helices

Umemura¹,

Matsumoto²,

Ohnishi³

et al. 2002

Journal of Biological Chemistry

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The two major chemoreceptors of Escherichia coli, Tsr and Tar, mediate opposite responses to the same changes in cytoplasmic pH (pH i ). We set out to identify residues involved in pH i sensing to gain insight into the general mechanisms of signaling employed by the chemoreceptors. did not change the polarity but altered the time course of pH i response. These results suggest that the electrostatic properties of a short cytoplasmic region within the linker region that connects the second transmembrane helix to the first methylation helix is critical for switching the signaling state of the chemoreceptors during pH sensing. Similar conformational changes of this region in response to external ligands may be critical components of transmembrane signaling.Many biological processes, such as enzyme reactions and interactions between proteins, are influenced by pH. Therefore, cells have to sense and adapt to changes in extracellular and intracellular pH. Despite the accumulated knowledge about pH-dependent regulation in a wide variety of organisms, the molecular mechanisms of pH sensing are still poorly understood.Behavioral responses of Escherichia coli and Salmonella typhimurium to changes in pH provide a convenient system for studying the pH-sensing mechanism. These bacteria show repellent responses to weak acids and attractant responses to weak bases (1, 2). These responses are generated by decreases and increases of cytoplasmic pH (pH i ). 1 The changes in pH i were documented by 31 P nuclear magnetic resonance spectroscopy (3, 4). Usually, pH i in E. coli is maintained at around 7.5 over a range of extracellular pH (pH o ) values from 5.0 to 9.0 (3, 5). However, this strong pH i homeostasis can be disrupted by the addition of weak acids or weak bases to the culture medium. When pH o is lower than pH i , weak acids can traverse the membrane in their protonated (uncharged) form and release protons in the cytoplasm to decrease pH i . Similarly, when pH o is higher than pH i , weak bases can traverse the membrane in deprotonated (uncharged) forms and capture protons in the cytoplasm to increase pH i . These changes in pH i correlate well with tactic responses to weak acids and weak bases (4).The signal transduction pathway for chemotaxis in E. coli and S. typhimurium has been extensively studied at the molecular level (for reviews, see Refs. 6 -9). These organisms have a set of related methyl-accepting chemoreceptors that includes the serine receptor Tsr and the aspartate receptor Tar. These receptors have a remarkable ability to sense a variety of stimuli, including chemoattractants, chemorepellents, temperature, and pH.Tar and, presumably, the other chemoreceptors exist as a homodimer of about 60-kDa subunits (10). The dimeric cytoplasmic domains form stable complexes with the histidine kinase CheA and the adaptor protein CheW (11,12). Furthermore, the receptors, together with the CheA and CheW proteins, cluster at a cell pole (13).CheA phosphorylates itself and then serves as a phosphodonor for the response regul...

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“…A number of functional hybrid histidine kinases have also been constructed by fusing the sensor module of one histidine kinase with the transmitter module of another histidine kinase at the HAMP linker region (NarQ-NarX, NarX-NarQ, and NarX-CpxA fusions) or by replacing the HAMP linker of one histidine kinase (NarX) with the HAMP linker of another histidine kinase (CpxA) (13). In addition, functional hybrid chemoreceptors have been constructed in which Tar-Tsr (14), Tap-Tar (15), and Trg-Tsr (16) fusions are made using the Tsr, Tar, and Tsr linkers, respectively, and a Aer-Tsr fusion is made using the Aer linker (17). The ligand responsiveness of all these hybrid sensor proteins indicates that a common mechanism may be shared for signal transduction.…”

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confidence: 99%

The HAMP Linker in Histidine Kinase Dimeric Receptors Is Critical for Symmetric Transmembrane Signal Transduction

Zhu

Inouye

2004

Journal of Biological Chemistry

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The HAMP linker, a common structural element between a sensor and a transmitter module in various sensor proteins, plays an essential role in signal transduction. Here, by in vivo complementation experiments with Tar-EnvZ hybrid receptor mutants in which the HAMP linker forms a heterodimer with Tar and EnvZtype subunits, we found that mutations at one linker only affect the function of EnvZ in the same subunit. However, the same mutations affect the EnvZ function of both subunits when only a Tar or EnvZ-type HAMP linker is used. These results suggest that intersubunit interactions in the HAMP linker normally mediate signal transduction through both subunits in a sensor dimer, whereas the signal is asymmetrically transduced through the linker in a heterodimer. This is the first demonstration that two HAMP linkers in a sensor dimer are functionally coupled for normal signal transduction; however, this functional coupling can be reduced when the HAMP linkers lose their symmetric nature.The HAMP linker is widely found in histidine kinases, chemoreceptors, bacterial nucleotidyl cyclases, and phosphatases (1-3). Although the primary sequence homology among predicted HAMP linkers is low, they all share a similar helix-turnhelix fold based on secondary structure prediction. A cysteinescanning study on the Tar linker supports this model of HAMP linker structure (4).Genetic analysis found a number of mutations clustered in the HAMP linker of various sensor proteins, which usually lead to biased signaling modes (5-9). This suggests that the HAMP linker plays an active role in signal transduction rather than being just a simple structural element connecting the sensor and transmitter modules of sensor proteins. However, the exact function of the HAMP linker on signal transduction remains to be determined.Functional hybrid histidine kinases have been constructed by fusing the sensor module of chemoreceptors (also called methyl-accepting chemotaxis proteins) to the transmitter module of histidine kinase EnvZ using the HAMP linker from either protein. In Taz1, the sensor module of chemoreceptor Tar is fused to the transmitter module of EnvZ using the Tar linker (10). In Trz, the sensor module of chemoreceptor Trg is fused to the transmitter module of EnvZ using the Trg linker (11). In Tez1A1 and Tez1PQ, the sensor module of Tar is fused to the transmitter module of EnvZ using the EnvZ linker with one Ala insertion at the N-terminal end and the EnvZ linker with a Pro to Gln mutation at position 185 (the position number is based on EnvZ sequence), respectively (12). A number of functional hybrid histidine kinases have also been constructed by fusing the sensor module of one histidine kinase with the transmitter module of another histidine kinase at the HAMP linker region (NarQ-NarX, NarX-NarQ, and NarX-CpxA fusions) or by replacing the HAMP linker of one histidine kinase (NarX) with the HAMP linker of another histidine kinase (CpxA) (13). In addition, functional hybrid chemoreceptors have been constructed in which Tar-Tsr (14), ...

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Chimeric chemosensory transducers of Escherichia coli.

Cited by 135 publications

References 31 publications

Structure of a conserved receptor domain that regulates kinase activity: the cytoplasmic domain of bacterial taxis receptors

Structure of a conserved receptor domain that regulates kinase activity: the cytoplasmic domain of bacterial taxis receptors

Sensing of Cytoplasmic pH by Bacterial Chemoreceptors Involves the Linker Region That Connects the Membrane-spanning and the Signal-modulating Helices

The HAMP Linker in Histidine Kinase Dimeric Receptors Is Critical for Symmetric Transmembrane Signal Transduction

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