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J. Biol. Chem., Vol. 282, Issue 47, 34120-34128, November 23, 2007

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The CheC Phosphatase Regulates Chemotactic Adaptation through CheD^*

From the Department of Biochemistry, Colleges of Medicine and Liberal Arts and Sciences, University of Illinois, Urbana, Illinois 61801

The bacterial chemotaxis system is one of the most extensively studied signal transduction systems in biology. The response regulator CheY controls flagellar rotation and is phosphorylated by the CheA histidine kinase to its active form. CheC is a CheY-P phosphatase, and this activity is enhanced in a CheC-CheD heterodimer. CheC is also critical for chemotactic adaptation, the return to the prestimulus system state despite persistent attractant concentrations. Here, CheC point mutants were examined in Bacillus subtilis for in vivo complementation and in vitro activity. The mutants were identified separating the three known abilities of CheC: CheD binding, CheY-P binding, and CheY-P phosphatase activity. Remarkably, the phosphatase ability was not as critical to the in vivo function of CheC as the ability to bind both CheY-P and CheD. Additionally, it was confirmed that CheY-P increases the affinity of CheC for CheD, the later of which is known to be necessary for receptor activation of CheA. These data suggest a model of CheC as a CheY-P-induced regulator of CheD. Here, CheY-P would cause CheC to sequester CheD from the chemoreceptors, inducing adaptation of the chemotaxis system. This model represents the first plausible means for feedback from the output of the system, CheY-P, to the receptors.

Received for publication, August 3, 2007 , and in revised form, August 17, 2007.

^* This work was supported by National Institutes of Health Grant RO1GM54365 (to G. W. O.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ Present address: Dept. of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037.

² To whom correspondence should be addressed: University of Illinois, 506 S. Matthews, 190 MSB, Urbana, IL 61801. Tel.: 217-333-9098 or 217-333-0268; Fax: 217-333-8868; E-mail: ordal{at}uiuc.edu.

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