6gq8

Publication Abstract from PubMed

Superoxide reductases (SORs) are enzymes that detoxify the superoxide anion through its reduction to hydrogen peroxide, that exist both in prokaryotes and eukaryotes. The substrate is transformed at an iron catalytic center, pentacoordinated in the ferrous state by four histidines and one cysteine. SORs have a highly conserved motif -(E)(K)HxP-, in which the glutamate is associated with a redox-driven structural change, completing the octahedral coordination of the iron in the ferric state, whereas the lysine may be responsible for stabilization and proton donation to catalytic intermediates. We aimed to understand at the structural level the role of these two residues, by determining the X-ray structures of the SORs from the hyperthermophilic archaea Ignicoccus hospitalis and Nanoarchaeum equitans that lack the quasi-conserved lysine or glutamate, respectively, albeit having catalytic rate constants similar to the canonical enzymes, as we previously demonstrated. Furthermore, we have determined the crystal structure of the E23A mutant of I. hospitalis SOR, which mimics several enzymes that lack both residues. The structures revealed distinct structural arrangements of the catalytic centre that simulate several catalytic cycle intermediates, namely the reduced and the oxidized forms, and the glutamate-free and deprotonated ferric forms. Moreover the structure of the I. hospitalis SOR provides evidence for the presence of an alternative lysine close to the iron center in the reduced state that may functionally substitute the "canonical" lysine.

Insights into the structures of superoxide reductases from the symbionts Ignicoccus hospitalis and Nanoarchaeum equitans.,Romao CV, Matias PM, Sousa CM, Pinho FG, Pinto AF, Teixeira M, Bandeiras TM Biochemistry. 2018 Jun 25. doi: 10.1021/acs.biochem.8b00334. PMID:29939726^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.