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Title: Superoxide reduction by a superoxide reductase lacking the highly conserved lysine residue

Superoxide reductases (SORs) are the most recently identified superoxide detoxification systems, being found in microorganisms from the three domains of life. These enzymes are characterized by a catalytic mononuclear iron site, with one cysteine and four histidine ligands of the ferrous active form. A lysine residue in the –EKHVP– motif, located close to the active site, has been considered to be essential for the enzyme function, by contributing to the positive surface patch that attracts the superoxide anion and by controlling the chemistry of the catalytic mechanism through a hydrogen bond network. However, we show here that this residue is substituted by non-equivalent amino acids in several putative SORs from Archaea and unicellular Eukarya. In this work, we focus on mechanistic and spectroscopic studies of one of these less common enzymes, the SOR from the hyperthermophilic crenarchaeon Ignicoccus hospitalis. We employ pulse radiolysis fast kinetics and spectroscopic approaches to study the wild-type enzyme (₋E₂₃T₂₄HVP₋), and two mutants, T24K and E23A, the later mimicking enzymes lacking both the lysine and glutamate (a ferric ion ligand) of the motif. The efficiency of the wild type protein and mutants in reducing superoxide is comparable to other SORs, revealing the robustness of these enzymesmore » to single mutations.« less
Authors:
 [1] ;  [2] ;  [3] ;  [1] ;  [1] ;  [4] ;  [1] ;  [1]
  1. Univ. Nova de Lisboa, Oeiras (Portugal)
  2. Brookhaven National Lab. (BNL), Upton, NY (United States)
  3. Univ. Nova de Lisboa, Oeiras (Portugal); Karolinska Inst., Stockholm (Sweden)
  4. Univ. Regensburg, Regensburg (Germany)
Publication Date:
OSTI Identifier:
1182506
Report Number(s):
BNL--107428-2015-JA
Journal ID: ISSN 0949-8257; R&D Project: CO-004; KC0304030
Grant/Contract Number:
SC00112704
Type:
Accepted Manuscript
Journal Name:
JBIC. Journal of Biological Inorganic Chemistry
Additional Journal Information:
Journal Volume: 20; Journal Issue: 1; Journal ID: ISSN 0949-8257
Publisher:
Springer
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY laser electron accelerator facility; superoxide; oxidative stress; superoxide reductase; Ignicoccus