Plants can produce their own set of defense molecules in an attempt to survive under stressed conditions. Dehydrins play a considerable role in protecting the plants under varied stress situations. We have isolated a novel SK3 type dehydrin from Sorghum capable of protecting the enzyme lactate dehydrogenase in vitro under both cold and high temperature. This protein showed non-canonical migration in a sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) due to the high hydrophilicity of the protein. The high percentage of glycine and histidine residues present in the protein sequence is responsible for the radical scavenging activity of the protein. The protein also exhibited binding affinity to metal ions owing to the histidine-rich motifs, therefore chelating the metal ions and making them unavailable to systems responsible for generation of reactive oxygen species (ROS). In the presence of specific metal ions, the protein showed reversible aggregation with certain degree of protease resistivity along with induction of secondary structures. The resistivity of the protein to degradation might be implicated in stress situations, thus leading to an increase in the shelf life of the protein. Association with metal ions like copper and zinc at a fairly low concentration increased the protective effect of the SbDHN2 protein for lactate dehydrogenase (LDH) activity to a considerable extent. The synthesis of this dehydrin in stressed plants might help the plant in rendering stress tolerance.
Keywords: Abnormal migration; Dehydrin; Protease resistivity; Radical scavenging; Sorghum bicolor.