, Volume 55, Issue 2, pp 225-230
Date: 04 Jan 2013

NMR structure note: a defective isoform and its activity-improved variant of a type III antifreeze protein from Zoarces elongates Kner

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Biological context

Antifreeze proteins (AFPs) produced in various cold-adapted animals and plants can specifically bind to ice crystals and inhibit their growth (Fletcher et al. 2001; Graether and Sykes 2004). The ice-binding ability of AFPs depresses the freezing temperature (Tf) of water non-colligatively, which leads to the protection of cells and tissues from freezing. The level of Tf depression has been evaluated by measuring the Tf and melting temperature (Tm) for an ice crystal created in an aqueous solution of an AFP. The difference between these two temperatures is defined as the thermal hysteresis (TH), which is a measure of the AFP’s ice-growth inhibition. AFPs also modify the shape of an ice crystal uniquely, hexagonal bipyramid for example, in the temperature range of TH. These two activities have been assumed to be common for all AFPs; however, it has recently been found that they are not always the rule for every species, such as the AFP type III (denoted AFPIII) found in