Subfreezing temperatures pose a severe threat to the survival of organisms inhabiting polar and subpolar environments. Many organisms, including plants, insects and fish, have adapted and developed protective mechanisms which lower the risk of freezing. Certain fish produce antifreeze proteins, i.e. substances which lower the freezing points of their body fluids by binding to and inhibiting the growth of seed ice crystals. Similar compounds (thermal hysteresis proteins) are currently being isolated from plants and insects. Also, protein- crystal interactions are biologically common and important in processes such as biomineralization and calcification. This research project plans to investigate the structure-function relationship of several antifreeze proteins, characterize their unique activity and identify structural features or common motifs required for activity. The long- term objectives are to improve our understanding of the kinetic and thermodynamic aspects of the protein adsorption to ice in order to identify the source for the observed high binding affinity and mechanism of freezing point depression. The studies will increase our basic understanding on protein-surface and protein-crystal interactions, and are aimed to facilitate the engineering of antifreeze compounds for use in the cryogenic storage of cells, blood and organs, and for conferring freezing resistance to crop and food. My laboratory is dedicated to the structural and mechanistic characterization of a number of distinct classes of antifreeze proteins.
The specific aims of this stage of the project will be to utilize homonuclear and heteronuclear multi-dimensional NMR-spectroscopy in combination with site-specific mutagenesis, computational methods and crystallization experiments to: i) determine the three dimensional structure of Type 2 antifreeze protein from herring, ii) determine the solution structure of Type 2 antifreeze protein from sea raven, iii) to determine the structure of a thermal hysteresis protein from the beetle Tenebrio molitor, and iv) to investigate the protein-water and protein-ice interactions of these proteins.
