Interactions of intrinsically disordered Thellungiella salsuginea dehydrins TsDHN-1 and TsDHN-2 with membranes - Synergistic effects of lipid composition and temperature on secondary structure

Dehydrins are intrinsically disordered (unstructured) proteins that are expressed in plants experiencing stressful conditions such as drought or low temperature. Dehydrins are typically found in the cytosol and nucleus, but also associate with chloroplasts, mitochondria, and the plasma membrane. Although their role is not completely understood, it has been suggested that they stabilize proteins or membrane structures during environmental stress, the latter association mediated by formation of amphipathic α-helices by conserved regions called the K-segments. Theilungieila salsuginea is a crucifer that thrives in the Canadian sub-Arctic (Yukon Territory) where it grows on saline-rich soils and experiences periods of both extreme cold and drought. We have cloned and expressed in Escherichia coli two dehydrins from this plant, denoted TsDHN-1 (acidic) and TsDHN-2 (basic). Here, we show using transmission-Fourier transform infrared (FTIR) spectroscopy that ordered secondary structure is induced and stabilized in these proteins by association with large unilamellar vesicles emulating the lipid compositions of plant plasma and organellar membranes. Moreover, this induced folding is enhanced at low temperatures, lending credence to the hypothesis that dehydrins stabilize plant outer and organellar membranes in conditions of cold.