The quaternary structure of streptavidin in urea.

摘要: We report on the interactions of urea and guanidinium salts with streptavidin. Gel filtration chromatography in 0, 4, 6, 7 M indicates that streptavidin tetramer remains intact urea. Biotin alters electrophoretic mobility whether or not 6 is present. The intrinsic fluorescence increased blue-shifted changes indicate absence unfolding. A conformational response to possible, but much change due binding as a weak biotin analog (Ka approximately 1.3 M-1). resistance structural perturbation by reflects stability streptavidin's anti-parallel beta-barrel motif. Unfolding sluggish hydrochloride (half-time, 50 days). After thiocyanate unfolding, can be refolded, unfolding refolding transitions are centered at different concentrations perturbant. Slow 15th power dependence concentration, may partially responsible for noncoincidence processes. Nonequilibrium behavior also seen urea, native does unfold unfolded refold. Refolding occur lower Guanidinium only slowly unfolds biotin-streptavidin complex. In presence biotin, refold