Biophysical characterization and folding studies of plant protease, wrightin: identification of folding intermediate under different conditions.

Wrightin, a serine protease from Wrightia tinctoria, has been used as model system to examine structure-function and stability. Our studies show high stability of the enzyme with major elements of secondary structure being beta-sheets. Under neutral conditions the enzyme is stable in 8 M urea and high temperature. GuHCl induced unfolding of wrightin at lower pH cannot be satisfactorily fit to a two state model for unfolding. Multiple intermediates were identified during unfolding of wrightin. Further, two intermediates, early and late are identified in the urea induced unfolding pathway at pH 3.0. Spectroscopic properties of intermediate states are analyzed and interpreted.