title: Guanidine hydrochloride stabilization of a partially unfolded intermediate during the reversible denaturation of protein disulfide isomerase.
abstract: The reversible denaturation of protein disulfide isomerase proceeds through intermediates that are stabilized by interaction with guanidine hydrochloride. At pH 7.5, the equilibrium denaturation by urea is completely reversible and the transition can be reasonably well-described by a two-state model involving only native and denatured forms. In comparison, the equilibrium denaturation by guanidine hydrochloride occurs in two distinct steps. In the presence of a low constant amount of guanidine hydrochloride (0.5-1.4 M), urea denaturation also becomes biphasic, suggesting the accumulation of an intermediate species that is stabilized by specific interaction with guanidine hydrochloride but not by high concentrations of other salts or other denaturants.
authors.affiliation: Verna and Marrs McLean Department of Biochemistry, Baylor College of Medicine, Houston, TX 77030.
authors.forename: N A
authors.initials: NA
authors.lastname: Morjana
authors.forename: B J
authors.initials: BJ
authors.lastname: McKeone
authors.forename: H F
authors.initials: HF
authors.lastname: Gilbert
mesh_terms: D000818:Animals; D002151:Calorimetry; D002417:Cattle; D004795:Enzyme Stability / Q000187:drug effects; D019791:Guanidine; D006146:Guanidines / Q000494:pharmacology*; D007527:Isoenzymes / Q000737:chemistry* / Q000302:isolation & purification; D007535:Isomerases / Q000737:chemistry* / Q000302:isolation & purification; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D011489:Protein Denaturation; D019704:Protein Disulfide-Isomerases; D017510:Protein Folding; D014508:Urea
chemical_list: D006146:Guanidines; D007527:Isoenzymes; D014508:Urea; D007535:Isomerases; D019704:Protein Disulfide-Isomerases; D019791:Guanidine