Meeting Abstract

P2.21  Tuesday, Jan. 5  Diverse antifreeze proteins as models for adaptive protein evoltion CZIKO, Paul A.; University of Oregon pcziko@uoregon.edu

The threat of organismal freezing in the ice-laden Polar marine environment has driven the evolution of specific biochemical adaptations in the resident fauna. Unlike hypoosmotic teleost fishes which are known to be protected against freezing by antifreeze proteins, marine invertebrates are isoosmotic to seawater and therefore have long been considered immune to freezing due to the colligative freezing-point depression of their fluids. Although being isoosmotic may partially explain survival of invertebrates in Polar waters, the countless species that encounter ice and supercooled water require supplementary adaptations. Expression of antifreeze proteins (AFPs) may be one mechanism by which invertebrates survive the harsh polar environment. My surveys of many polar macroinvertebrates have revealed a diverse but entirely Polar distribution of AFPs. My initial characterizations of invertebrate AFPs suggest that they may have evolved from a common protein ancestor in some lineages, but other species appear to have arrived at independent solutions to the problem of freezing-avoidance. The evolution of antifreeze proteins in response to environmental cooling over geologic timescales is an exemplary example of adaptive protein evolution. AFP purification and sequencing followed by genomic analyses in a comparative and phylogenetic context is expected to result in the reconstruction of the pathways of protein evolution in these models.