Attraction by Repellents: An Error in Sensory Information Processing by Bacterial Mutants

Muskavitch, Marc A. T.; Kort, Edward N.; Springer, Martin S.; Goy, Michael F.; Adler, Julius

doi:10.1126/science.351803

Cited by 40 publications

(37 citation statements)

References 16 publications

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“…As with Biochemistry: Kleene et al (12) nor repellents (18), gave methylation rates only slightly different from the control rate (2% and 4% changes, respectively). (23).] The mixture of repellents inhibited methylation of MCP I primarily, as expected from in vivo results (2).…”

supporting

confidence: 49%

Attractants and repellents influence methylation and demethylation of methyl-accepting chemotaxis proteins in an extract of Escherichia coli.

Kleene¹,

Hobson²,

Adler³

1979

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

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During bacterial chemotaxis, attractants and repellents alter the methylation levels of the methyl-accepting chemotaxis proteins (MCPs). These methylation levels represent a balance between two enzymatic processes: methylation and demethylation. In vivo experiments previously have shown that chemoeffectors influence the demethylation process; effects on the methylation system have not been reported. Here we show that in a cell-free extract of Escherichia coli both methylation and demethylation of the MCPs are affected by attractants and repellents. Attractants enhance methylation and inhibit demethylation. Repellents inhibit methylation and stimulate demethylation. The cell-free system provides an opportunity for further study of the mechanisms by which attractants and repellents influence the levels of methylation of the MCPs.As part of the mechanism of chemotaxis by Escherichia coli, attractants and repellents change the methylation levels of a set of cytoplasmic membrane proteins, the methyl-accepting chemotaxis proteins (MCPs) (1-6). These methylation levels are the result of two enzymatic processes: methyl groups are transferred from S-adenosylmethionine to the MCPs by a methylation system (7), whereas methyl groups are removed by a demethylation system to produce methanol (8,9). When the two systems are in balance, the level of methylation remains constant, but the individual methyl groups turn over (1,9,10). When an attractant is presented, the methylation level rises, and this higher value is maintained as long as the attractant is present (4). The rise coincides with a transient shut-off of demethylation (10); whether there is also an increase in methylation activity is unknown. Conversely, when a repellent is presented, the methylation level drops, and this lower value is maintained as long as the repellent is present (4). An increase in demethylation activity in response to repellents has been observed (10), but effects on methylation have not been reported.By using modifications of previously reported in vitro systems (7, 8), we have been able to examine the effects of attractants and repellents on both methylation and demethylation in a cell-free extract of E. coli. We have shown in such extracts that demethylation is inhibited by attractants and stimulated by repellents, as has been reported in intact bacteria (10). In addition, we find that methylation in these extracts is stimulated by attractants and inhibited by repellents. These results may help to explain the effects of chemoeffectors on levels of MCP methylation in intact bacteria. Nuclear. L-Arginine, L-aspartic acid, L-leucine, L-lysine, and L-serine were purchased from Calbiochem. a-Aminoisobutyric acid and a-methyl-DL-aspartic acid were obtained from Sigma.All other chemicals were reagent grade. Acetic acid, a-methylaspartic acid, and aspartic acid were used as the sodium salts.Bacteria. All strains used are E. coli K-12 derivatives and have been described previously. RP487 (9) is the chemotactically wild-type parent of AW663...

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supporting

confidence: 49%

Attractants and repellents influence methylation and demethylation of methyl-accepting chemotaxis proteins in an extract of Escherichia coli.

Kleene¹,

Hobson²,

Adler³

1979

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

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“…This does not seem to be a case of inversion of the sort first noted by Muskavitch et al (23), which resulted from the properties of, for example, TsrE in the absence of TarE, since tsrE tarE tape mutants responded to phenol as a repellent, yet their methylation levels were too low to be detected either with or without phenol stimulation. We suspect that the response may result from a general perturbation of the energy state of the cell, possibly related to the mechanism of aerotaxis (32); at concentrations at which phenol elicited a behavioral response, there was often a noticeable reduction in swimming speed.…”

Section: Resultsmentioning

confidence: 87%

“…What then was the cause of the opposite effect of phenol for E. coli and S. typhimurium? Inversion of responses has been observed in other situations when the receptor that normally handles the relevant stimulus is defective or missing (21,23), and it has been suggested that the mechanism may involve compensating effects on other methyl-accepting receptors. We might have been inclined to propose a similar type of effect, involving the amounts and interactions of known receptors, had we not obtained biochemical evidence for a methyl-accepting receptor in S. typhimurium that is specifically responsible for the repellent response to phenol in that species.…”

Section: Resultsmentioning

confidence: 99%

Phenol: a complex chemoeffector in bacterial chemotaxis

Imae¹,

Oosawa²,

Mizuno³

et al. 1987

J Bacteriol

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Earlier observations that phenol is a repellent for Salmonella typhimurium but an attractant for Escherichia coli were confirmed. This behavioral difference was found to correlate with a difference in the effect phenol had on receptor methylation levels; it caused net demethylation in S. typhimurium but net methylation in E. coli.On the basis of mutant behavior and measurement of phenol-stimulated methylation, the attractant response of E. coli was shown to be mediated principally by the Tar receptor. In S. typhimurium, two receptors were found to be sensitive to phenol, namely, an unidentified receptor, which mediated the repellent response and showed phenol-stimulated demethylation; and the Tar receptor, which (as with E. colt) mediated the attractant response and showed phenol-stimulated methylation. In wild-type S. typhimurium, the former receptor dominated the Tar receptor, with respect to both behavior and methylation changes. However, when the amount of Tar receptor was artificially increased by the use of Tar-encoding plasmids, S. typhimurium cells exhibited an attractant response to phenol. No protein analogous to the phenol-specific repellent receptor was evident in E. coli, explaining the different behavioral responses of the two species toward phenol.

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“…Reversed phenotypes have previously been reported for MCP Tar-and Tsr-mediated responses to membrane-permeating weak acids, oxygen tension, and changes in temperature (9,23,25,26,39). Mutations causing these phenotypes have been found in TM-2, the junction between the HAMP linker AS-2 and the adaptation domains, and the adaptation domains of these MCPs.…”

Section: Vol 185 2003mentioning

confidence: 93%

Mutational Analysis of a Conserved Signal-Transducing Element: the HAMP Linker of theEscherichia coliNitrate Sensor NarX

Appleman

Stewart

2003

J Bacteriol

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The HAMP linker, a predicted structural element observed in sensor proteins from all domains of life, is proposed to transmit signals between extracellular sensory input domains and cytoplasmic output domains. HAMP (histidine kinase, adenylyl cyclase, methyl-accepting chemotaxis protein, and phosphatase) linkers are located just inside the cytoplasmic membrane and are projected to form two short amphipathic ␣-helices (AS-1 and AS-2) joined by an unstructured connector. The presumed helices are comprised of hydrophobic residues in heptad repeats, with only three positions exhibiting strong conservation. We generated missense mutations at these three positions and throughout the HAMP linker in the Escherichia coli nitrate sensor kinase NarX and screened the resulting mutants for defective responses to nitrate. Most missense mutations in this region resulted in a constitutive phenotype mimicking the ligand-bound state, and only one residue (a conserved Glu before AS-2) was essential for HAMP linker function. We also scanned the narX HAMP linker with an overlapping set of seven-residue deletions. Deletions in AS-1 and the connector resulted in constitutive phenotypes. Two deletions in AS-2 resulted in a novel reversed response phenotype in which the response to ligand was the opposite of that seen for the narX ؉ strain. These observations are consistent with the proposed HAMP linker structure, show that the HAMP linker plays an active role in transmembrane signal transduction, and indicate that the two amphipathic ␣-helices have different roles in signal transduction.Two-component regulatory systems are used by all domains of life to sense and respond to environmental changes (37). These systems stereotypically consist of a sensor kinase and a cytoplasmic response regulator. One prototypical class of sensor kinases shares the structure of methyl-accepting chemotaxis proteins (MCPs), which are homodimers located in the cytoplasmic membrane. This structure consists of a short amino-terminal cytoplasmic segment, a transmembrane ␣-helix (TM-1), an external ligand-binding sensory input domain, a second transmembrane ␣-helix (TM-2), and a cytoplasmic output module (13).Sequence comparisons and mutational analysis of sensor kinases and MCPs identified a common structural element hypothesized to transmit signals between external input domains and cytoplasmic output modules (2,17,42). This element is called the HAMP (histidine kinase, adenylyl cyclase, MCP, and phosphatase) linker, or the P-type linker. More than 95% of HAMP linkers identified by similarity to the Escherichia coli EnvZ HAMP linker are from sensor kinases or MCPs; all five MCPs and 15 of the 30 known sensor kinases of E. coli contain HAMP linkers (Fig. 1) (2).The HAMP linker comprises the approximately 50 amino acyl residues distal to TM-2. This region includes two sequences of hydrophobic amino acids in a heptameric arrangement, with phased spacing of hydrophobic residues characteristic of amphipathic ␣-helices. These sequences have been named amphipathic se...

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Attraction by Repellents: An Error in Sensory Information Processing by Bacterial Mutants

Cited by 40 publications

References 16 publications

Attractants and repellents influence methylation and demethylation of methyl-accepting chemotaxis proteins in an extract of Escherichia coli.

Attractants and repellents influence methylation and demethylation of methyl-accepting chemotaxis proteins in an extract of Escherichia coli.

Phenol: a complex chemoeffector in bacterial chemotaxis

Mutational Analysis of a Conserved Signal-Transducing Element: the HAMP Linker of theEscherichia coliNitrate Sensor NarX

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