Structure and Function of an Aromatic Ensemble That Restricts the Dynamics of the Hydrophobic Core of a Designed Helix-Loop-Helix Dimer

摘要

GTD-43, a polypeptide with 43 amino acid residues, has been designed to fold into a hairpin helix-loop- helix motif that can dimerize to form a four-helix bundle. The mean residue ellipticity is -21000 deg cm~2 dmol~-1, and the magnitude is independent of pH in the interval of 2.4-4.6. The chemical shift dispersion of the amide proton and methyl regions of the ~1H NMR spectrum is only slightly less than that of Interleukin-4, a naturally occurring four-helix bundle, and much larger than those reported for molten globule structures.