An antifreeze protein folds with an interior network of more than 400 semi-clathrate waters

Science. 2014 Feb 14;343(6172):795-8. doi: 10.1126/science.1247407.


When polypeptide chains fold into a protein, hydrophobic groups are compacted in the center with exclusion of water. We report the crystal structure of an alanine-rich antifreeze protein that retains ~400 waters in its core. The putative ice-binding residues of this dimeric, four-helix bundle protein point inwards and coordinate the interior waters into two intersecting polypentagonal networks. The bundle makes minimal protein contacts between helices, but is stabilized by anchoring to the semi-clathrate water monolayers through backbone carbonyl groups in the protein interior. The ordered waters extend outwards to the protein surface and likely are involved in ice binding. This protein fold supports both the anchored-clathrate water mechanism of antifreeze protein adsorption to ice and the water-expulsion mechanism of protein folding.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alanine / chemistry
  • Animals
  • Antifreeze Proteins, Type I / chemistry*
  • Crystallography, X-Ray
  • Fish Proteins / chemistry*
  • Flounder
  • Ice
  • Protein Folding*
  • Protein Structure, Secondary
  • Water / chemistry


  • Antifreeze Proteins, Type I
  • Fish Proteins
  • Ice
  • Water
  • Alanine

Associated data

  • PDB/4KE2