Many marine fish species produce biological antifreeze peptides (AFPs) as a means of freezing avoidance in the presence of sub-zero environmental temperatures. AFPs bind to and prevent the growth of minute internalized ice crystals, thereby inhibiting the freezing of extracellular fluids. To elucidate the molecular evolution of AFPs, the AFP system of an antarctic eel pout (Pachycara brachycephalus, family Zoarcidae) was characterized and compared to related AFP-producing species. Protein and mRNA analyses indicate that the AFP complement of P. brachycephalus is composed of one predominant AFP (94% total) and a host of at least 10 minor isoform s (6% total), each 63 amino acids in length and bearing >80% sequence similarity to the others. Genomic DNA studies show P. brachycephalus to contain an AFP gene family of about 68 member genes, each gene studied bearing an exon-intron-exon motif common to nearly all known zoarcid AFP genes. The AFP genes of P. brachycephalus appear to be irregularly spaced throughout the genome (similar to the atlanric Macrmoarces americanus) ana not in 8-kbp tandem repeating units (as in the arctic Anarhichus lupus and antarctic Licodychthys dearborn,). The similar protein and gene structures, contrasted by diverse gene arrangements in the zoarcid genomes, suggest that AFP gene duplication occurred after speciation from a zoarcid ancestor containing an AFP-like gene. Thus, AFP gene duplication appears to have occurred in parallel among zoarcid species, although the mechanisms of gene duplication and diversification in each species have been independent.
|Original language||English (US)|
|State||Published - Dec 1 1996|
ASJC Scopus subject areas
- Molecular Biology