The use of osmolytes to facilitate protein NMR spectroscopy

Summary

A method of stabilizing folded proteins is described, which allows NMR studies under conditions where a protein would normally be unfolded. This enables stable proteins to be examined at elevated temperatures, or spectra recorded on samples that are insufficiently stable under normal conditions. Up to two molar perdeuterated glycine, a potent osmolyte, can be added to aqueous protein NMR samples without altering the folded three-dimensional structure or function of the protein. However, the stability of the folded form is dramatically increased. This is illustrated for the protein lysozyme at high temperature (348 K) where the structural integrity is destroyed in standard aqueous solution, but is retained in the osmolyte solution. We hope that the technique will be of value to those studying by NMR the structural biology of protein fragments and mutants, which are often of reduced stability compared with the original proteins.