3-DIMENSIONAL STRUCTURE OF CHEMOTACTIC CHE-Y PROTEIN IN AQUEOUS-SOLUTION BY NUCLEAR-MAGNETIC-RESONANCE METHODS

The three-dimensional structure of chemotactic Che Y protein from Esch erichia coli in aqueous solution has been determined by nuclear magnet ic resonance (NMR) spectroscopy combined with restrained molecular dyn amics calculations. A total of 20 converged structures were computed f rom 1545 conformationally relevant distance restraints derived from 18 58 unambiguously assigned NOE cross-correlations. The resulting averag e pairwise root-mean-square deviation is 1.03 Angstrom for the backbon e atoms and 1.69 Angstrom for all heavy atoms. If residues in the regi ons structurally least defined (1 to 5, 47 to 50, 76 to 79, 88 to 91 a nd 124 to 129) are excluded from the analysis, the root-mean-square de viations are reduced to 0.53 Angstrom and 1.23 Angstrom, respectively. The solution structure is closely similar to the refined X-ray crysta l structure, except in the regions found to be less defined by NMR spe ctroscopy. The root-mean-square deviation between the average solution structure and the X-ray crystal structure is 0.92 Angstrom for the ba ckbone residues (2 to 129). The highly refined solution structure dete rmined herewith provides an essential background to delineate function ally important conformational changes brought about by different effec tors.