H-1 AND C-13 NMR ASSIGNMENTS AND MOLECULAR MODELING OF A MINOR-GROOVEDNA-BINDING PEPTIDE FROM THE HMG-I PROTEIN

The HMG-I subfamily of high mobility group (HMG) chromatin proteins co nsists of DNA-binding proteins that preferentially bind to stretches o f A . T-rich sequence both in vitro and in vivo. Recently, members of the HMG-I family have been suggested to bind in vitro to the narrow mi nor groove of A . T-DNA by means of an 11 amino acid peptide binding d omain (BD) which, because of its predicted structure, is called the 'A . T-hook motif [Reeves, R. & Nissen, M. (1990) J. Biol. Chem. 265, 85 73-8582], and would appear to be crescent-shaped. A BD peptide with 13 amino-acid residues was synthesized and examined by proton and carbon -13 nuclear magnetic resonance (NMR) spectroscopy. The peptide contain s four proline residues, and on the basis of NOEs and C-13 chemical sh ifts was found to exist in an all-trans conformation. Molecular modell ing based on this result provides evidence for a dynamic equilibrium b etween turn-like conformations in solution, the most populated of whic h is likely to be an S-shaped conformer, on the basis of amide exchang e data. (C) Munksgaard 1995.