title: Refolding of recombinant sulphonated procathepsin S and of reduced chicken cystatin; implications for renaturation experiments.
abstract: Kinetic stopped-flow measurements of refolding of the recombinant sulphonated procathepsin S from 6 M urea are presented. The experiments were performed using intrinsic tryptophan fluorescence and fluorescence of the hydrophobic probe 1-anilino-naphthalene-8-sulfonate (ANS). Initially, (t1/2 = 3 +/- 1 ms) an intermediate with increased ANS fluorescence and protected tryptophan environment is formed. Much later, a slow increase in ANS fluorescence occurs with no accompanying changes in tryptophan fluorescence. The reaction of the slow ANS fluorescence increase correlates with the rate of aggregation as shown by the size exclusion chromatography (SEC). For comparison, the folding reactions of the reduced chicken cystatin were measured, both, by intrinsic tryptophan and extrinsic ANS fluorescence. An early intermediate forms very fast in the refolding of reduced chicken cystatin on 6-fold dilution from 5.7 M GuHCl (t1/2 = 5 +/- 2 ms), similarly to that observed for the sulphonated procathepsin S. ANS fluorescence and tryptophan fluorescence decrease further (t1/2 = 100 +/- 50 ms) leading to a late, 'more structured' intermediate which is prone to dimerization.
authors.affiliation: Department of Biochemistry and Molecular Biology, J. Stefan Institute, Ljubljana, Slovenia. eva.zerovnik@ijs.si
authors.forename: E
authors.initials: E
authors.lastname: Zerovnik
authors.forename: G
authors.initials: G
authors.lastname: Kopitar
authors.forename: J
authors.initials: J
authors.lastname: Kos
authors.forename: V
authors.initials: V
authors.lastname: Turk
mesh_terms: D000818:Animals; D002403:Cathepsins / Q000737:chemistry* / Q000235:genetics; D002645:Chickens; D015891:Cystatins / Q000737:chemistry* / Q000235:genetics; D017510:Protein Folding; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics
chemical_list: D015891:Cystatins; D011994:Recombinant Proteins; D002403:Cathepsins; C028217:cathepsin S