Adaptation of Arctic Fish

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Introduction Arctic fish display a remarkable case of adaptation, living in in low temperatures around 0˚C with areas of ice that can be -1.9˚C (DeVries, 1971). The ability for Arctic fish to thrive in such a low temperature environment is made possible by a class of proteins called Antifreeze proteins. Antifreeze proteins (AFPs) and Antifreeze glycoproteins (AFGPs) are polypeptides that are biosynthesized in animals, plants and fungi that prevent ice crystal formation (Griffith & Ewart, 1995). The most widely accepted mechanism for the prevention of ice formation by AFPs and AFGPs is called the adsorption-inhibition mechanism, which describes that the protein binds to water molecules and separates water molecules at a certain distance. This separation distance is large enough to inhibit ice crystal formation and prevent recrystallization (Raymond et al., 1977). The complexity of AFPs and AFGPs provoke several important questions regarding their origins, such as: From where did AFPs and AFGPs originate? How conserved are AFPs and AFGPs among different species of polar fish, are they conserved? Through what mechanisms have antifreeze proteins, and antifreeze glycoproteins evolved? What environmental or ecological stresses influenced the proliferation of AFPs and AFGPs in cold-water fish? The stunning amount of diversity found in antifreeze proteins is evident of a fascinating evolutionary story. Exploring the phylogenetic and molecular data from different species of cold-water fish is a common starting point for determining the origins of antifreeze proteins. Antifreeze proteins can be divided into two groups, the AFPs and AFGPs. Of the AFPs, there are currently four known types: I, II, III and IV (Cheng et al., 1998). By examining... ... middle of paper ... ... similarities between proteins exhibiting homology, and inspecting the AFP nucleic acid sequence in comparison with proteins showing similarities. The driving force for most of these evolutionary events is supported by colder climates. Oceanic cooling most certainly added selective pressures towards polar fish, bearing in mind the evidence that suggests protein homology, it is possible to propose that the aforementioned AFPs are derived from different proteins seen today. Environment stress influencing AFP and AFGP proliferation is most supported by glaciation and cooling periods. Evidence from Pleistocene cooling events covers several AFPs and the AFGPs as a relevant selective pressure. As the ever-expanding amount of protein sequences become more available, I also expect the accuracy for pinpointing protein homology to elucidate explicit evolutionary mechanisms.

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