Secondary Structure Changes and Thermal Stability of Plasma Membrane Proteins of Wheat Roots in Heat Stress

Abstract

The wheat roots membrane separates the cell from the environment around it and encloses the cell contents. The pro-tein secondary structure and thermal stability of the plasma membrane of wheat root have been characterized in D₂O buffer from 20°C to 90°C by Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Quantitative analysis of the amide I band (1700 - 1600 cm^–1) showed that the plasma membrane proteins contains 41% α-helix, 16% β-sheet, 18% turn, and 25% disorder structures at 20°C. At elevated temperatures from 25°C up to 90°C, the α-helix and the β-sheet structure unfold into turns and the disorder structure, with a major conformational transition occurring at 50°C. There is a rapid decline in H⁺-ATPase activity of plasma membrane from 35°C to 55°C and it remain very low level H⁺-ATPase activity of PM from 55°C to 90°C. Therefore the protein conformational transition was one of reasons of loses H⁺-ATPase activity of plasma membrane.