Crystal structure of an antifreeze polypeptide and its mechanistic implications

• DOI: 10.1038/333232a0
• Publication Date: 2003-06-12T21:57:10Z
• Authors: D. S. C. Yang; M. Sax; A. Chakrabartty; C. L. Hew
• Keywords: Models, Molecular; 0301 basic medicine; Protein Conformation; Molecular Sequence Data; Fishes; Flounder; 03 medical and health sciences; Species Specificity; X-Ray Diffraction; Antifreeze Proteins; Flatfishes; Animals; Amino Acid Sequence; Glycoproteins

The X-ray crystallographic structure of an antifreeze polypeptide from the fish winter flounder, has been determined at 2.5 A by an analysis of the Patterson function. This is the first report of a polypeptide of this size that is a single alpha-helix. A proposed mechanism of antifreeze binding to ice surfaces is given which requires: first, that the dipole moment from the helical structure dictates the preferential alignment of the peptide to the c-axis of ice nuclei; second, amphiphilicity of the helix; and third, torsional freedom of the side chains to facilitate hydrogen bonding to ice surfaces.