Quantitative and qualitative analysis of type III antifreeze protein structure and function

J Biol Chem. 1999 Apr 23;274(17):11842-7. doi: 10.1074/jbc.274.17.11842.

Abstract

Some cold water marine fishes avoid cellular damage because of freezing by expressing antifreeze proteins (AFPs) that bind to ice and inhibit its growth; one such protein is the globular type III AFP from eel pout. Despite several studies, the mechanism of ice binding remains unclear because of the difficulty in modeling the AFP-ice interaction. To further explore the mechanism, we have determined the x-ray crystallographic structure of 10 type III AFP mutants and combined that information with 7 previously determined structures to mainly analyze specific AFP-ice interactions such as hydrogen bonds. Quantitative assessment of binding was performed using a neural network with properties of the structure as input and predicted antifreeze activity as output. Using the cross-validation method, a correlation coefficient of 0.60 was obtained between measured and predicted activity, indicating successful learning and good predictive power. A large loss in the predictive power of the neural network occurred after properties related to the hydrophobic surface were left out, suggesting that van der Waal's interactions make a significant contribution to ice binding. By combining the analysis of the neural network with antifreeze activity and x-ray crystallographic structures of the mutants, we extend the existing ice-binding model to a two-step process: 1) probing of the surface for the correct ice-binding plane by hydrogen-bonding side chains and 2) attractive van der Waal's interactions between the other residues of the ice-binding surface and the ice, which increases the strength of the protein-ice interaction.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antifreeze Proteins
  • Glycoproteins / chemistry*
  • Glycoproteins / genetics
  • Glycoproteins / metabolism*
  • Models, Molecular
  • Mutagenesis, Site-Directed
  • Neural Networks, Computer
  • Protein Conformation
  • Structure-Activity Relationship

Substances

  • Antifreeze Proteins
  • Glycoproteins

Associated data

  • PDB/1B7I
  • PDB/1B7J
  • PDB/1B7K
  • PDB/1EKL
  • PDB/1JAB
  • PDB/1MSJ
  • PDB/2AME
  • PDB/2JIA
  • PDB/2MSJ
  • PDB/2SPG
  • PDB/3AME
  • PDB/4AME
  • PDB/6AME
  • PDB/7AME
  • PDB/8AME
  • PDB/8MSI
  • PDB/9AME
  • PDB/9MSI