SOLUTION STRUCTURE OF THE DNA-BINDING DOMAIN AND MODEL FOR THE COMPLEX OF MULTIFUNCTIONAL HEXAMERIC ARGININE REPRESSOR WITH DNA

The structure of the monomeric DNA-binding domain of the Escherichia c oli arginine repressor, ArgR, determined by NMR spectroscopy, shows st ructural homology to the winged helix-turn-helix (wHTH) family, a moti f found in a diverse class of proteins including both gene regulators and gene organizers from prokaryotes and eukaryotes. Biochemical data on DNA binding by intact ArgR are used as constraints to position the domain on its DNA target and to derive a model for the hexamer-DNA com plex using the known structure of the L-arginine-binding domain. The s tructural independence of the wHTH fold may be important for multimeri c DNA-binding proteins that contact extended DNA regions with imperfec t match to consensus sequences, a feature of many wHTH-domain proteins .