Temperature-Induced Protein Conformational Changes in Barley Root Plasma Membrane-Enriched Microsomes

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Abstract
A protein spin label and lipid spin probes were used to study the temperature-dependent motion of protein and lipid, respectively, in barley (Hordeum vulgare L. cv Conquest) root plasma membrane-enriched microsomes. Using membranes from seedlings grown at 20°C, the temperature-dependence of the relative motion of membrane surface spin probes and a spin label covalently attached to membrane proteins suggested abrupt changes in the lipid and protein mobilities at about 12°C. Spin probe spin-spin exchange broadening and fluorescent probe eximer formation indicated apparent temperature-induced alterations in probe lateral diffusion within the membrane at about 12 to 14°C. The results suggest the presence of temperature-induced quasicrystalline lipid clusters which may influence the activity of membrane-bound enzymes.