Ndi1 is a special type-II complex I nicotinamide-adenine-dinucleotide (NADH):ubiquinone (UQ) oxidoreductase in the yeast respiratory chain, with two bound UQs (UQ_I and UQ_II) mediating electron transfer from flavin cofactors to ubiquinone, in the absence of Fe-S chains. Here, we elucidate the underlying mechanism of electron transfer in Ndi1 through temperature-dependent Electron Spin Resonance (ESR) experiments in conjunction with quantum chemical calculations. It is revealed that electron transfer is mediated by antiferromagnetic (AFM) interactions between flavin-adenosine-dinucleotide (FAD) and UQ_I and between UQ_I and UQ_II. The π-stacking interactions among the aromatic complexes also enhance the through-space electron transfer. The FAD/UQ_I pair works as a rectifier converting double-electron co-transfer into sequential single-electron transfer events. The results not only expand our understanding on the observed AFM interactions among p-orbital aromatic mixed-stack in proteins, but also provide significant insights into the fabrication of materials with special magnetic properties using biological samples.

• PMID: 28134365
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Journal Article

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Wu K, Li W, Yu L, Tong W, Feng Y, Ling S, Zhang L, Zheng X, Yang M, Tian C

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