PMID:11742065

Citation	Sourjik, V and Berg, HC (2002) Receptor sensitivity in bacterial chemotaxis. Proc. Natl. Acad. Sci. U.S.A. 99:123-7
Abstract	Chemoreceptors in Escherichia coli are coupled to the flagella by a labile phosphorylated intermediate, CheY approximately P. Its activity can be inferred from the rotational bias of flagellar motors, but motor response is stochastic and limited to a narrow physiological range. Here we use fluorescence resonance energy transfer to monitor interactions of CheY approximately P with its phosphatase, CheZ, that reveal changes in the activity of the receptor kinase, CheA, resulting from the addition of attractants or repellents. Analyses of cheR and/or cheB mutants, defective in receptor methylation/demethylation, show that response sensitivity depends on the activity of CheB and the level of receptor modification. In cheRcheB mutants, the concentration of attractant that generates a half-maximal response is equal to the dissociation constant of the receptor. In wild-type cells, it is 35 times smaller. This amplification, together with the ultrasensitivity of the flagellar motor, explains previous observations of high chemotactic gain.
Links	PubMed PMC117525 Online version:10.1073/pnas.011589998
Keywords	Bacterial Physiological Phenomena; Bacterial Proteins; Chemotaxis; Dose-Response Relationship, Drug; Membrane Proteins/chemistry; Membrane Proteins/physiology; Methylation; N-Methylaspartate/analogs & derivatives; N-Methylaspartate/pharmacology; Phosphorylation; Protein Binding; Spectrometry, Fluorescence; Time Factors
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