Isolation and characterization of type I antifreeze proteins from Atlantic snailfish (Liparis atlanticus) and dusky snailfish (Liparis gibbus)

Antifreeze proteins (AFPs) were isolated from the blood plasma of Atlantic snailfish Liparis atlanticus and dusky snailfish Liparis gibbus, which belong to the Teleost family Cyclopteridae. a close relative of sculpins. Using a combination of gel filtration chromatography and reversed-phase HPLC, proteins were purified to individual peaks. Atlantic snailfish plasma contained two different proteins (MW=9344, 9415) while dusky snailfish plasma contained five protein isoforms (MW = 951-9814), as determined by mass spectrometry. Further characterization revealed that these proteins are rich in alanine (> 50 mol%), and have a-helical secondary structure that can undergo reversible thermal denaturation. Thermal hysteresis activities of these proteins were similar to each other but lower than the major type I AFPs from winter flounder. Results of this study have indicated that although the AFPs from snailfish are significantly larger than previously described type I AFPs, they share enough characteristics to be classified in this group. (C) 2001 Elsevier Science B.V. All rights reserved.