Winter flounder antifreeze proteins: a multigene family.

The nucleotide sequence of a cDNA clone of winter flounder antifreeze protein was determined by the dideoxynucleotide method. The sequence would predict a protein of 91 amino acids composed of a prepropeptide of 38 amino acids and a mature protein of 53 amino acids, which includes four complete 11-amino acid repeats. This predicted sequence corresponds to an antifreeze protein of intermediate size which is one 11-amino acid repeat longer than the smallest antifreeze proteins found in the serum of winter flounder during the cold season. Southern blot hybridization analysis of winter flounder genomic DNA with radioactive cDNA probes reveals a multigene family of potential antifreeze protein genes. This conclusion is supported by amino acid sequence analysis of several serum antifreeze proteins.