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Journal of Bacteriology, November 2004, p. 7556-7563, Vol. 186, No. 22
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.22.7556-7563.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Ligand-Specific Activation of Escherichia coli Chemoreceptor Transmethylation

Frances M. Antommattei,1 Jennifer B. Munzner,2,{dagger} and Robert M. Weis1,2*

Department of Chemistry,1 Program in Molecular and Cell Biology, University of Massachusetts, Amherst, Massachusetts2

Received 7 July 2004/ Accepted 13 August 2004

Adaptation in the chemosensory pathways of bacteria like Escherichia coli is mediated by the enzyme-catalyzed methylation (and demethylation) of glutamate residues in the signaling domains of methyl-accepting chemotaxis proteins (MCPs). MCPs can be methylated in trans, where the methyltransferase (CheR) molecule catalyzing methyl group transfer is tethered to the C terminus of a neighboring receptor. Here, it was shown that E. coli cells exhibited adaptation to attractant stimuli mediated through either engineered or naturally occurring MCPs that were unable to tether CheR as long as another MCP capable of tethering CheR was also present, e.g., either the full-length aspartate or serine receptor (Tar or Tsr). Methylation of isolated membrane samples in which engineered tethering and substrate receptors were coexpressed demonstrated that the truncated substrate receptors (trTsr) were efficiently methylated in the presence of tethering receptors (Tar with methylation sites blocked) relative to samples in which none of the MCPs had tethering sites. The effects of ligand binding on methylation were investigated, and an increase in rate was produced only with serine (the ligand specific for the substrate receptor trTsr); no significant change in rate was produced by aspartate (the ligand specific for the tethering receptor Tar). Although the overall efficiency of methylation was lower, receptor-specific effects were also observed in trTar- and trTsr-containing samples, where neither Tar nor Tsr possessed the CheR binding site at the C terminus. Altogether, the results are consistent with a ligand-induced conformational change that is limited to the methylated receptor dimer and does not spread to adjacent receptor dimers.

* Corresponding author. Mailing address: Department of Chemistry, LGRT 701, 710 North Pleasant St., University of Massachusetts, Amherst, MA 01003-9336. Phone: (413) 545-0464. Fax: (413) 545-4490. E-mail: rmweis{at}chem.umass.edu.

{dagger} Present address: Pfizer Central Research, Candidate Enhancement Group, Groton, CT 06340.

Journal of Bacteriology, November 2004, p. 7556-7563, Vol. 186, No. 22
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.22.7556-7563.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Besschetnova, T. Y., Montefusco, D. J., Asinas, A. E., Shrout, A. L., Antommattei, F. M., Weis, R. M. (2008). Receptor density balances signal stimulation and attenuation in membrane-assembled complexes of bacterial chemotaxis signaling proteins. Proc. Natl. Acad. Sci. USA 105: 12289-12294 [Abstract] [Full Text]  
  • Wolanin, P. M., Baker, M. D., Francis, N. R., Thomas, D. R., DeRosier, D. J., Stock, J. B. (2006). Self-assembly of receptor/signaling complexes in bacterial chemotaxis. Proc. Natl. Acad. Sci. USA 103: 14313-14318 [Abstract] [Full Text]  


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