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Journal of Bacteriology, May 2006, p. 3299-3307, Vol. 188, No. 9
0021-9193/06/$08.00+0     doi:10.1128/JB.188.9.3299-3307.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Mutational Analysis of the Chemoreceptor-Coupling Domain of the Escherichia coli Chemotaxis Signaling Kinase CheA

Jinshi Zhao and John S. Parkinson*

Biology Department, University of Utah, Salt Lake City, Utah 84112

Received 21 May 2005/ Accepted 16 February 2006

During chemotactic signaling by Escherichia coli, autophosphorylation of the histidine kinase CheA is coupled to chemoreceptor control by the CheW protein, which interacts with the C-terminal P5 domain of CheA. To identify P5 determinants important for CheW binding and receptor coupling control, we isolated and characterized a series of P5 missense mutants. The mutants fell into four phenotypic groups on the basis of in vivo behavioral and protein stability tests and in vitro assays with purified mutant proteins. Group 1 mutants exhibited autophosphorylation and receptor-coupling defects, and their CheA proteins were subject to relatively rapid degradation in vivo. Group 1 mutations were located at hydrophobic residues in P5 subdomain 2 and most likely caused folding defects. Group 2 mutants made stable CheA proteins with normal autophosphorylation ability but with defects in CheW binding and in receptor-mediated activation of CheA autophosphorylation. Their mutations affected residues in P5 subdomain 1 near the interface with the CheA dimerization (P3) and ATP-binding (P4) domains. Mutant proteins of group 3 were normal in all tests yet could not support chemotaxis, suggesting that P5 has one or more important but still unknown signaling functions. Group 4 mutant proteins were specifically defective in receptor-mediated deactivation control. The group 4 mutations were located in P5 subdomain 1 at the P3/P3' interface. We conclude that P5 subdomain 1 is important for CheW binding and for receptor coupling control and that these processes may require substantial motions of the P5 domain relative to the neighboring P3 and P4 domains of CheA.

* Corresponding author. Mailing address: Biology Department, 257 South 1400 East, University of Utah, Salt Lake City, UT 84112. Phone: (801) 581-7639. Fax: (801) 581-4668. E-mail: Parkinson{at}Biology.Utah.Edu.

Journal of Bacteriology, May 2006, p. 3299-3307, Vol. 188, No. 9
0021-9193/06/$08.00+0     doi:10.1128/JB.188.9.3299-3307.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Zhao, J., Parkinson, J. S. (2006). Cysteine-Scanning Analysis of the Chemoreceptor-Coupling Domain of the Escherichia coli Chemotaxis Signaling Kinase CheA.. J. Bacteriol. 188: 4321-4330 [Abstract] [Full Text]  


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