1. Enzyme structure captures four cysteines aligned for disulfide relay.
- Author
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Gat Y, Vardi-Kilshtain A, Grossman I, Major DT, and Fass D
- Subjects
- Animals, Biocatalysis, Crystallography, X-Ray, Cysteine chemistry, Disulfides chemistry, Models, Molecular, Protein Conformation, Quantum Theory, Rats, Cysteine metabolism, Disulfides metabolism, Thioredoxins chemistry, Thioredoxins metabolism
- Abstract
Thioredoxin superfamily proteins introduce disulfide bonds into substrates, catalyze the removal of disulfides, and operate in electron relays. These functions rely on one or more dithiol/disulfide exchange reactions. The flavoenzyme quiescin sulfhydryl oxidase (QSOX), a catalyst of disulfide bond formation with an interdomain electron transfer step in its catalytic cycle, provides a unique opportunity for exploring the structural environment of enzymatic dithiol/disulfide exchange. Wild-type Rattus norvegicus QSOX1 (RnQSOX1) was crystallized in a conformation that juxtaposes the two redox-active di-cysteine motifs in the enzyme, presenting the entire electron-transfer pathway and proton-transfer participants in their native configurations. As such a state cannot generally be enriched and stabilized for analysis, RnQSOX1 gives unprecedented insight into the functional group environments of the four cysteines involved in dithiol/disulfide exchange and provides the framework for analysis of the energetics of electron transfer in the presence of the bound flavin adenine dinucleotide cofactor. Hybrid quantum mechanics/molecular mechanics (QM/MM) free energy simulations based on the X-ray crystal structure suggest that formation of the interdomain disulfide intermediate is highly favorable and secures the flexible enzyme in a state from which further electron transfer via the flavin can occur., (© 2014 The Protein Society.)
- Published
- 2014
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