Molten globule as an intermediate on the human prostatic phosphatase folding pathway.

Abstract

Human prostatic acid phosphatase (hPAP, EC.3.1.3.2), a secretory homodimeric protein was denatured in 6 M urea, pH 2.5, and refolded by dilution at pH 7.2 with recovery of the enzymatic activity and dimeric structure. Circular dichroism, intrinsic fluorescence and chromatographic analysis of renaturating protein suggested that the kinetic intermediate of the hPAP folding is a monomer which displays a molten globule state (R. Kuciel, A. Mazurkiewicz & W.S. Ostrowski, 1996, Int. J. Biol. Macromol. 18, 167-175). To confirm these data experiments were performed to estimate the interaction of the renaturating protein with dyes and amphipathic lipid structures. Increased binding of the hydrophobic probe 1-anilinonaphthalene-8-sulfonate and Congo Red to the refolding enzyme supported the existence of molten globule state with the relaxed beta-structure in the renaturating protein. Presence of liposomes, included in the renaturation mixture as a model of acid phospholipid, resulted in perturbations of the human PAP refolding process. Some folding intermediates were bound to phosphatidylserine liposomes or, alternatively, water soluble, inactive aggregates were formed.