The structures of T871 phosphono-CheY and T871/Y106W phosphono-CheY help to explain their binding affinities to the FliM and CheZ peptides

摘要

CheY is a response regulator in bacterial chemotaxis. Escherichia coli CheY mutants T871 and T871/Y106W CheY are phosphorylatable on Asp57 but unable to generate clockwise rotation of the flagella. To understand this phenotype in terms of structure, stable analogs of the two CheY-P mutants were synthesized: T871 phosphono-CheY and T871 phosphono-CheY. Dissociation constants for peptides derived from flagellar motor protein FliM and phosphatase CheZ were determined for phosphono-CheY and the two mutants. The peptides bind phosphono-CheY almost as strongly as CheY-P; however, they do not bind T871 phosphono-CheY or T871/Y106W phosphono-CheY, implying that the mutant Proteins cannot bind FliM OF CheZ tightly in vivo. The structures of T871 phosphono-CheY and T871/Y106W phosphono-CheY were solved to resolutions of 1.8 and 2.4 angstrom, respectively. The increased bulk of 187 forces the side-chain of Y106 or W106, into a more solvent-accessible conformation, which occludes the peptide-binding site. (C) 2008 Elsevier Inc. All rights reserved.