Abstract

This is the first experimental evidence of an equilibrium intermediate in the unfolding of triosephosphate isomerase (TIM). The reversible unfolding of S. cerevisiae TIM induced by both guanidine­ HCl (Gdn-HCl) and urea, are apparently monophasic when followed by spectroscopic techniques. Kinetic analysis and ANS binding data confirm a two-state transition in urea. nevertheless, in Gdn-HCl they indicate an intermediate. Hydrodynamic properties of the intermediate are consistent with a compact monomer.