Latent Ice Recrystallization Inhibition Activity inNonantifreeze Proteins: Ca2+-Activated Plant Lectins andCation-Activated Antimicrobial Peptides

摘要

Organisms living in polar regions have evolved a series of antifreeze (glyco) proteins (AFGPs) to enable them to survive by modulating the structure of ice. These proteins have huge potential for use in cellular cryopreservation, ice-resistant surfaces, frozen food, and cryosurgery, but they are limited by their relatively low availability and questions regarding their mode of action. This has triggered the search for biomimetic materials capable of reproducing this function. The identification of new structures and sequences capable of inhibiting ice growth is crucial to aid our understanding of these proteins. Here, we show that plant c-type lectins, which have similar biological function to human c-type lectins (glycan recognition) but no sequence homology to AFPs, display calcium-dependent ice recrystallization inhibition (IRI) activity. This IRI activity can be switched on/off by changing the Ca²⁺ concentration. To show that more (nonantifreeze) proteins may exist with the potential to display IRI, a second motif was considered, amphipathicity. All known AFPs have defined hydrophobic/hydrophilicdomains, rationalizing this choice. The cheap, and widely used, antimicrobialNisin was found to have cation-dependent IRI activity, controlledby either acid or addition of histidine-binding ions such as zincor nickel, which promote its amphipathic structure. These resultsdemonstrate a new approach in the identification of antifreeze proteinmimetic macromolecules and may help in the development of syntheticmimics of AFPs.