title: Theoretical insights into the mechanism of redox switch in heat shock protein Hsp33.
abstract: Heat shock protein 33 (Hsp33) is activated in the presence of H2O2 by a very interesting redox switch based on a tetra-coordinated zinc-cysteine complex present in the fully reduced and inactive protein form. The oxidation of this zinc center by H2O2 induces formation of two S-S bridges and the zinc release followed by the protein unfolding. We report here a theoretical study of the step-by-step sequence of the overall process starting with the oxidation of the first cysteine residue and ending with the zinc release. Each reaction step is characterized by its Gibbs free energy barrier (∆G (‡)). It is predicted that the first reaction step consists in the oxidation of Cys263 by H2O2 which is by far the most reactive cysteine (∆G (‡) = 15.4 kcal mol(-1)). The next two reaction steps are the formation of the first S-S bridge between Cys263 and Cys266 (∆G (‡) = 13.6 kcal mol(-1)) and the oxidation of Cys231 by H2O2 (∆G (‡) = 20.4 kcal mol(-1)). It is then shown that the formation of the second S-S bridge (Cys231-Cys233) before the zinc release is most unlikely (∆G (‡) = 34.8 kcal mol(-1)). Instead, the release of zinc just after the oxidation of the third cysteine (Cys231) is shown to be thermodynamically (dissociation Gibbs free energy ∆G d = 6.0 kcal mol(-1)) and kinetically (reaction rate constant k d ≈ 10(6) s(-1)) favored. This result is in good agreement with the experimental data on the oxidation mechanism of Hsp33 zinc center available to date.
authors: Laboratoire Chrono Environnement UMR CNRS 6249, University of Franche-Comté, 16 route de Gray, 25030, Besançon Cedex, France, mironel.enescu@univ-fcomte.fr.
authors: Mironel
authors: M
authors: Enescu
authors: Rima
authors: R
authors: Kassim
authors: Christophe
authors: C
authors: Ramseyer
authors: Bruno
authors: B
authors: Cardey
mesh_terms: D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000378:metabolism; D010084:Oxidation-Reduction; D013816:Thermodynamics
chemical_list: D029968:Escherichia coli Proteins; C492165:HSP33 protein, E coli; D006360:Heat-Shock Proteins
references: J Biol Chem. 2000 Jun 23;275(25):18759-66
references: 10764757
references: Inorg Chem. 2011 Jun 20;50(12):5407-16
references: 21598974
references: Biochemistry. 2012 Jan 10;51(1):475-86
references: 22208667
references: J Biol Inorg Chem. 2013 Mar;18(3):333-42
references: 23334196
references: J Phys Chem B. 2007 Apr 26;111(16):4200-10
references: 17394305
references: Curr Opin Struct Biol. 2013 Jun;23(3):436-42
references: 23477949
references: J Biol Chem. 2004 May 7;279(19):20529-38
references: 15023991
references: Nat Struct Mol Biol. 2007 Jun;14(6):556-63
references: 17515905
references: Structure. 2001 May 9;9(5):377-87
references: 11377198
references: Antioxid Redox Signal. 2009 May;11(5):997-1014
references: 18999917
references: J Mol Biol. 1995 Nov 10;253(5):799-812
references: 7473753
references: Biochemistry. 2000 Apr 18;39(15):4207-16
references: 10757967
references: J Phys Chem B. 2006 Aug 17;110(32):16066-81
references: 16898764
references: J Mol Model. 2007 Dec;13(12):1173-213
references: 17828561
references: Antioxid Redox Signal. 2011 Mar 15;14(6):1065-77
references: 20799881
references: J Mol Biol. 1976 May 15;103(2):227-49
references: 985660
references: Biochim Biophys Acta. 2014 Aug;1844(8):1335-43
references: 24657586
references: Cell. 2008 Nov 14;135(4):691-701
references: 19013278
references: Proteins. 2005 Nov 15;61(3):669-73
references: 16167343
references: Free Radic Biol Med. 1999 Aug;27(3-4):322-8
references: 10468205
references: Chemphyschem. 2005 Jun 13;6(6):1175-80
references: 15883994