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Oxidation of the N‐terminal domain of the wheat metallothionein E c ‐1 leads to the formation of three distinct disulfide bridges
Author(s) -
Tarasava Katsiaryna,
Chesnov Serge,
Freisinger Eva
Publication year - 2016
Publication title -
peptide science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.22849
Subject(s) - chemistry , proteolysis , metallothionein , metal , redox , cysteine , disulfide bond , metal ions in aqueous solution , crystallography , stereochemistry , inorganic chemistry , zinc , biochemistry , organic chemistry , enzyme
Metallothioneins (MTs) are low molecular weight proteins, characterized by a high cysteine content and the ability to coordinate large amounts of d 10 metal ions, for example, Zn(II), Cd(II), and Cu(I), in form of metal‐thiolate clusters. Depending on intracellular conditions such as redox potential or metal ion concentrations, MTs can occur in various states ranging from the fully metal‐loaded holo‐ to the metal‐free apo‐form. The Cys thiolate groups in the apo‐form can be either reduced or be involved in disulfide bridges. Although oxidation‐mediated Zn(II) release might be a possible mechanism for the regulation of Zn(II) availability by MTs, no concise information regarding the associated pathways and the structure of oxidized apo‐MT forms is available. Using the well‐studied Zn 2 γ‐E c ‐1 domain of the wheat Zn 6 E c ‐1 MT we attempt here to answer several question regarding the structure and biophysical properties of oxidized MT forms, such as: (1) does disulfide bond formation increase the stability against proteolysis, (2) is the overall peptide backbone fold similar for the holo‐ and the oxidized apo‐MT form, and (3) are disulfide bridges specifically or randomly formed? Our investigations show that oxidation leads to three distinct disulfide bridges independently of the applied oxidation conditions and of the initial species used for oxidation, that is, the apo‐ or the holo‐form. In addition, the oxidized apo‐form is as stable against proteolysis as Zn 2 γ‐E c ‐1, rendering the currently assumed degradation of oxidized MTs unlikely and suggesting a role of the oxidation process for the extension of protein lifetime in absence of sufficient amounts of metal ions. © 2016 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 295–308, 2016.