Antifreeze protein pseudogenes

Abstract

Three members, 11-3, F2 and 5a, of the type-I antifreeze protein (AFP) multigene family in winter flounder were sequenced. All three belong to the subset of AFP genes that are linked, but irregularly spaced, and show significant differences from the functional genes in tandem repeats. 11-3 and F2 appear to be pseudogenes. Their intron, 3'-exon and 3'-flanking DNAs are similar to those of other AFP genes, but their 5'-exon is either missing or extensively modified, and has stop codons present in all three reading frames. Based on a comparison of intron sequences of family members, 11-3/F2 may represent a residual progenitor AFP gene which was duplicated after reaching pseudogene status. The third gene, 5a, is remarkable in having a 3'-exon that encodes an exceptionally long, Ala-rich sequence that lacks any semblance of the 11-amino acid repeats found in 11-3, F2 and functional AFP genes. 5a might also be a pseudogene, because its presumed TATA box appears to have mutated.