Hyperactive antifreeze protein from fish contains multiple ice-binding sites

Biochemistry. 2008 Feb 19;47(7):2051-63. doi: 10.1021/bi7020316. Epub 2008 Jan 29.


Antifreeze proteins (AFPs) are produced to prevent freezing in many fish species that are exposed to icy seawater. There are a number of nonhomologous types of AFPs, diverse in both sequence and structure, which share the function of binding to ice and inhibiting its growth. We recently discovered a hyperactive AFP in the winter flounder and related species that is many-fold more active than other fish AFPs. Like the 3-4-kDa type I AFPs, it is alanine-rich and highly helical, but this 17-kDa protein is considerably larger and forms a dimer. We have sequenced the cDNA encoding this new AFP to gain insight into its structure and evolutionary relationship to the type I AFP family. The gene is clearly homologous to the righteye flounder type I AFP genes. Thus we have designated this protein "hyperactive type I AFP" (hyp-type I). The sequence of hyp-type I AFP supports a structural model in which two extended 195-amino acid alpha-helices form an amphipathic homodimer with a series of linked Ala- and Thr-rich patches on the surface of the dimer, each of which resembles ice-binding sites of type I AFPs. The superior activity of hyp-type I AFP may derive from the large combined surface area of the ice-binding sites, recognition of multiple planes of ice, and protection of the basal plane from ice growth.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Antifreeze Proteins / chemistry
  • Antifreeze Proteins / genetics
  • Antifreeze Proteins / metabolism*
  • Base Sequence
  • Binding Sites
  • DNA Primers
  • DNA, Complementary
  • Flounder
  • Ice*
  • Molecular Sequence Data
  • Peptide Mapping
  • Sequence Homology, Amino Acid
  • Sequence Homology, Nucleic Acid
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization


  • Antifreeze Proteins
  • DNA Primers
  • DNA, Complementary
  • Ice