Distinguishing multiple chemotaxis Y protein conformations with laser-polarized 129Xe NMR.

The chemical shift of the ¹²⁹Xe NMR signal has been shown to be extremely sensitive to the local environment around the atom and has been used to follow processes such as ligand binding by bacterial periplasmic binding proteins. Here we show that the ¹²⁹Xe shift can sense more subtle changes: magnesium binding, BeF₃⁻ activation, and peptide binding by the Escherichia coli chemotaxis Y protein. ¹H-¹⁵N correlation spectroscopy and X-ray crystallography were used to identify two xenon-binding cavities in CheY that are primarily responsible for the shift changes. One site is near the active site, and the other is near the peptide binding site. [ABSTRACT FROM AUTHOR]