Dioxygen and superoxide stability of metallopeptide based mimics of nickel containing superoxide dismutase: The influence of amine/amidate vs. bis-amidate ligation.

Dioxygen and superoxide stability of metallopeptide based mimics of nickel containing superoxide dismutase: The influence of amine/amidate vs. bis-amidate ligation.
J Inorg Biochem. 2013 Sep 21;129C:145-149
Authors: Shearer J
Abstract
Nickel containing superoxide dismutase (NiSOD) is a metalloenzyme that catalyzes the disproportionation of O2(-). In its reduced state, the Ni(II) ion is coordinated by two cis-cysteinates, an amine nitrogen and an amidate nitrogen atom. It thus bears a resemblance to the distal bis-cysteinate bis-amidate ligated nickel center of acetyl coenzyme A synthase. Using metallopeptide based NiSOD mimics derived from the first 12 residues of the NiSOD sequence we demonstrate that altering the primary coordination sphere from a bis-thiolate amine/amidate motif to a bis-thiolate bis-amidate motif changes the O2 and ROS stability of the metallopeptide. Using FT-IR, ESI-MS and S K-edge XAS we show that the bis-amidate bis-thiolate ligated metallopeptide {Ni(II)(SOD(m1)-Ac)} (SOD(m1)-Ac=AcHN-HCDLPCGVYSPA-COOH) undergoes oxidation at one thiolate ligand in the presence of O2, converting it into a coordinated sulfinate. Upon exposure of {Ni(II)(SOD(m1)-Ac)} to O2(-) the metallopeptide undergoes extensive sulfur oxidation. This can be contrasted with the unacylated metallopeptide {Ni(II)(SOD(m1))} which does not undergo sulfur based oxidation under these conditions. The biological implications of these findings are discussed.
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Source: Journal of Inorganic Biochemistry - September 21, 2013 Category: Biochemistry Authors: Shearer J Tags: J Inorg Biochem Source Type: research