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A.J. Kiss, A.Y. Mirarefi, S. Ramakrishnan, C.F. Zukoski, C.–H.C. Cheng, A.L. DeVries; Characterisation of the Eye Lens Crystallins from the Antarctic Toothfish, Dissostichus mawsoni . Invest. Ophthalmol. Vis. Sci. 2004;45(13):3968.
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Purpose: Fishes that inhabit the perennially sub–freezing (–2°C) water of the Southern Ocean surrounding the Antarctic continent are cold–adapted. The eye lens of the giant Antarctic Toothfish, Dissostichus mawsoni, is completely transparent at –2°C, whereas mammalian eye lenses are cold sensitive, displaying a phenomenon known as a cold–cataract at 20°C. It is one of the highly expressed proteins of the lens, a γ crystallin that is responsible for the onset of the mammalian cold–cataract. Methods: We have purified the toothfish crystallins by size fractionation into the three major groups; α, ß, and γ, and have characterised them via SDS–PAGE and immunoblot, finding α and γ crystallin to be the major components. Results: In vitro experiments with isolated crystallins have established that fish α crystallin is a chaperone protein. Dynamic Light Scattering (DLS) experiments have confirmed that during the chaperone process, the α crystallin increases in hydrodynamic diameter, presumably by interacting with the γ crystallin. However, in a cross–species assay, the cow (mammalian) α crystallin cannot effectively chaperone the cold–adapted toothfish γ crystallins. Initial cDNA cloning has indicated that toothfish γ crystallins are less hydrophobic than homologous cow γ crystallins. Conclusions: As chaperone activity involves hydrophobic interactions, which are less important at low temperatures, we propose that the absence of chaperone activity between toothfish γ crystallins and the cow α crystallin originates with the less hydrophobic and low temperature stabile toothfish γ crystallins. Using structure–function and molecular analyses of the cold stable lens from this natural "mutant", the Antarctic toothfish, we hope to elucidate areas of crystallin stability and structure that will be valuable in addressing cataracts in man.
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