title: Extraordinary μs-ms backbone dynamics in Arabidopsis thaliana peroxiredoxin Q.
abstract: Peroxiredoxin Q (PrxQ) isolated from Arabidopsis thaliana belongs to a family of redox enzymes called peroxiredoxins, which are thioredoxin- or glutaredoxin-dependent peroxidases acting to reduce peroxides and in particular hydrogen peroxide. PrxQ cycles between an active reduced state and an inactive oxidized state during its catalytic cycle. The catalytic mechanism involves a nucleophilic attack of the catalytic cysteine on hydrogen peroxide to generate a sulfonic acid intermediate with a concerted release of a water molecule. This intermediate is subsequently relaxed by the reaction of a second cysteine, denoted the resolving cysteine, generating an intramolecular disulfide bond and release of a second water molecule. PrxQ is recycled to the active state by a thioredoxin-dependent reduction. Previous structural studies of PrxQ homologues have provided the structural basis for the switch between reduced and oxidized conformations. Here, we have performed a detailed study of the activity, structure and dynamics of PrxQ in both the oxidized and reduced states. Reliable and experimentally validated structural models of PrxQ in both oxidation states were generated using homology based modeling. Analysis of NMR spin relaxation rates shows that PrxQ is monomeric in both oxidized and reduced states. As evident from R(2) relaxation rates the reduced form of PrxQ undergoes unprecedented dynamics on the slow μs-ms timescale. The ground state of this conformational dynamics is likely the stably folded reduced state as implied by circular dichroism spectroscopy. We speculate that the extensive dynamics is intimately related to the catalytic function of PrxQ.
authors.affiliation: Department of Chemistry, Umea University, Umea, Sweden.
authors.forename: Jörgen
authors.initials: J
authors.lastname: Adén
authors.forename: Marcus
authors.initials: M
authors.lastname: Wallgren
authors.forename: Patrik
authors.initials: P
authors.lastname: Storm
authors.forename: Christoph F
authors.initials: CF
authors.lastname: Weise
authors.forename: Alexander
authors.initials: A
authors.lastname: Christiansen
authors.forename: Wolfgang P
authors.initials: WP
authors.lastname: Schröder
authors.forename: Christiane
authors.initials: C
authors.lastname: Funk
authors.forename: Magnus
authors.initials: M
authors.lastname: Wolf-Watz
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000032:analysis / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D019906:Nuclear Magnetic Resonance, Biomolecular; D010084:Oxidation-Reduction; D054464:Peroxiredoxins / Q000032:analysis / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D017510:Protein Folding; D055550:Protein Stability; D017433:Protein Structure, Secondary; D013696:Temperature; D013816:Thermodynamics
chemical_list: D029681:Arabidopsis Proteins; D054464:Peroxiredoxins; C510753:peroxiredoxin Q, Arabidopsis