Native Dimer Stabilizes the Subunit Tertiary Structure of Porcine Class pi Glutathione S‐transferase

Abstract

Solvent‐induced unfolding of porcine class pi glutathione S‐transferase (pGST P1‐1), a homodimeric protein, was monitored under equilibrium conditions using different physicochemical parameters (tryptophan fluorescence, anisotropy, degree of tyrosine exposure, binding of 8‐anilino‐1‐naphthalenesulphonic acid, size‐exclusion HPLC). The coincidence of unfolding curves obtained with functional (enzyme activity) and structural probes (anisotropy), the absence of thermodynamically stable intermediates such as a folded monomer (determined by binding of 8‐anilino‐1‐naphthalenesulphonic acid and size‐exclusion HPLC), and the dependence of pGST P1‐1 stability upon protein concentration (measured with structural and functional probes), indicate a cooperative and concerted two‐state unfolding transition between native dimeric pGST P1‐1 and unfolded monomeric enzyme. Copyright © 1995, Wiley Blackwell. All rights reserved