1H- and 15N-NMR assignment and solution structure of the chemotactic Escherichia coli Che Y protein.

Che Y is a 129-residue parallel alpha/beta protein involved in bacterial chemotaxis. We have used this protein as a model to study the folding reaction of parallel alpha/beta proteins. As a first step we carried out the complete assignment of the 1H and 15N spectra from Escherichia coli Che Y protein on the basis of two-dimensional 1H homonuclear and 1H-15N heteronuclear experiments by using sequence-specific methods. Our assignments differ from the preliminary assignments made by Kar et al. [Kar, L., Matsumura, P. & Johnson, M.E. (1992) Biochem. J. 287, 521-531] of aromatic residues obtained by comparison of NOEs with short proton-proton distances in the crystal structure of Che Y. The analysis of the extension of the secondary elements, as well as a preliminary calculation of the three-dimensional structure, indicate that the solution structure is closely coincident with the single crystal structure determined by X-ray diffraction.