The role of the K2 dehydrin from Vitis riparia in the cryoprotection of lactate dehydrogenase

Hughes, Stephanie Lesia
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University of Guelph

This thesis focuses on the K2 dehydrin from 'Vitis riparia' (wild grape) and how it functions to protect the enzyme, lactate dehydrogenase (LDH) from freeze-thaw damage. Dehydrins are proteins which protect select plants from cold and dehydrative stress. The biochemical mechanism by which they protect proteins from dehydrative damage is not well characterized. These proteins are currently proposed to function by binding water and protecting cellular proteins and membranes. Initial research involved measuring the cryoprotective effect of K2 on LDH, which was found to be greater than that of our positive control, bovine serum albumin. Nuclear magnetic resonance was performed to establish which residues in K2 may be involved in these interactions; however, no interactions were observed. 1-anilinonaphthalene-8-sulfonic acid, gel filtration and light scattering were used to determine how K2 protected LDH from denaturation. The results showed that aggregation was a major cause of LDH denaturation. Current studies focus on dilution experiments to establish whether K 2 acts as a molecular shield to protect LDH during freeze-thaw, and salt cryoprotection assays to observe the importance of electrostatic interactions during protection.

K2 dehydrin, Vitis riparia, wild grape, lactate dehydrogenase, freeze-thaw damage, cryoprotective effect