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J. Bacteriol. doi:10.1128/JB.01414-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Interaction of CheY with the C-Terminal Peptide of CheZ

Center for Advanced Biotechnology and Medicine, 679 Hoes Lane, Piscataway, NJ 08854, USA; Department of Biochemistry, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA, 679 Hoes Lane, Piscataway, NJ 08854; Howard Hughes Medical Institute, 679 Hoes Lane, Piscataway, NJ 08854, USA

^* To whom correspondence should be addressed. Email: stock{at}cabm.rutgers.edu.

	Abstract

Chemotaxis, a means for motile bacteria to sense the environment and achieve directed swimming, is controlled by flagellar rotation. The primary output of the chemotaxis machinery is the phosphorylated form of the response regulator CheY (PCheY). The steady-state level of PCheY dictates the direction of rotation of the flagellar motor. The chemotaxis signal in the form of PCheY is terminated by the phosphatase CheZ. Efficient dephosphorylation of CheY by CheZ requires two distinct protein-protein interfaces: one involving the strongly conserved C-terminal helix of CheZ (CheZ_C) tethering the two proteins together and the other constituting an active site for catalytic dephosphorylation. In a previous work (Guhaniyogi J., Robinson V. L. and Stock A. M. 2006. J. Mol. Biol. 359: 624-645), we presented high-resolution crystal structures of CheY in complex with the CheZ_C peptide that revealed alternate binding modes subject to the conformational state of CheY. In this study, we report biochemical and structural data that support the alternate binding mode hypothesis and identify key recognition elements in the CheY-CheZ_C interaction. In addition, we present kinetic studies of CheZ_C-associated effect on CheY phosphorylation with its physiologically relevant phosphodonor, the histidine kinase CheA. Our results indicate mechanistic differences in phosphotransfer from the kinase CheA versus from small molecule phosphodonors explaining a modest 2-fold increase of CheY phosphorylation with the former, observed in this study, relative to a 10-fold increase previously documented with the latter.