Characterization of skin and plasma type I antifreeze proteins from Atlantic (Liparis atlanticus) and dusky (Liparis gibbus) snailfish

• Main Author: Evans, Robert Philip
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 2003
• Subjects: Newfoundland
• Online Access: https://research.library.mun.ca/10470/; https://research.library.mun.ca/10470/1/Evans_Robert.pdf

Atlantic snailfish (Liparis atlanticus) and dusky snailfish (Liparis gibbus) belong to a large family of benthic and pelagic marine fishes that inhabit northern regions of the Atlantic Ocean. Both species spawn during the winter months in ice-laden inshore coastal regions around Newfoundland. Due to their harsh winter environment, snailfish are prime candidates for production of antifreeze proteins (AFPs). -- Initial results confirmed that plasma from both species contain alanine rich, α-helical, type I AFPs that are significantly larger (>9.3 kDa) than all previously described type I AFPs. Surprisingly, their skin tissues produce AFPs that are identical to those which circulate in blood. While all snailfish consistently express antifreeze mRNA in skin tissue, there is extreme individual variation in liver expression - an unusual phenomenon that has never been reported previously. Molecular analyses revealed that snailfish AFPs are products of multi gene families that consist of at least ten gene copies per genome. It is unclear if liver and skin antifreeze mRNAs are expressed by the same gene or a separate subset of genes which is typical of other fish that produce skin-type AFPs. -- Although the 113 residue snailfish AFPs are unusually long, their amino acid composition, highly a-helical secondary structure and the bipyramidal ice-crystals they create are characteristic of all type I AFPs. However, unlike other type I AFPs, snailfish proteins do not contain any obvious amino acid repeats or a continuous hydrophobic face that typify the structure of most other type I AFPs. These structural differences might have implications for their ice crystal binding properties. Biochemical experiments demonstrated that physiological concentrations of normal salts are responsible for a significant increase in thermal hysteresis activity in antifreeze proteins and glycoproteins. The colligative effects of these salts can account for the supplementary freezing point depression of blood required to ensure survival of marine ...