DNA-binding mechanism of the monomeric orphan nuclear receptor NGFI-B

The 2.7 Angstrom X-ray crystal structure of the DNA-binding domain (DBD) of the orphan nuclear receptor, nerve growth factor-induced-B (NGFI-B), compl exed to its high-affinity DNA target, represents the first structure analys is of a nuclear receptor DBD bound as a monomer to DNA. The structure of th e core DBD and its interactions with the major groove of the DNA are simila r to previously crystallographically solved DBD-DNA complexes in this super family; however, residues C-terminal to this core form a separate and uniqu e substructure that interacts extensively and in a sequence-specific way wi th the minor groove of its DNA target, in particular with the characteristi c 3 A-T base-pair identity element that extends 5' to the usual nuclear rec eptor half-site (AGGTCA).