Low potential enzymatic hydride transfer via highly cooperative and inversely functionalized flavin cofactors

• Published in: Nature communications Vol. 10; no. 1; p. 2074
• Main Authors: Willistein, Max, Bechtel, Dominique F., Müller, Christina S., Demmer, Ulrike, Heimann, Larissa, Kayastha, Kanwal, Schünemann, Volker, Pierik, Antonio J., Ullmann, G. Matthias, Ermler, Ulrich, Boll, Matthias
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 06.05.2019; Nature Publishing Group; Nature Portfolio
• Subjects: 119/118; 631/45/173; 631/45/603; 631/535/1266; Adenine; Bacterial Proteins - chemistry; Bacterial Proteins - isolation & purification; Bacterial Proteins - metabolism; Binding sites; Biochemistry; Biodegradation; Biological activity; Biophysics; Chemistry; Coenzymes - chemistry; Coenzymes - metabolism; Cofactors; Computer applications; Computer Simulation; Crystal structure; Crystallography; Crystallography, X-Ray; Electron transfer; Electron Transport; Electrons; Enzymes; Flavin mononucleotide; Flavin-adenine dinucleotide; Flavins - chemistry; Flavins - metabolism; Histamine; Humanities and Social Sciences; Hydrides; Hydrophobicity; Models, Molecular; multidisciplinary; Naphthalene; Naphthalenes - chemistry; Naphthalenes - metabolism; Nicotinamide; Nicotinamide adenine dinucleotide; Organic chemistry; Oxidoreductases - chemistry; Oxidoreductases - isolation & purification; Oxidoreductases - metabolism; Protein Structure, Tertiary; Proteins; Recombinant Proteins - chemistry; Recombinant Proteins - isolation & purification; Recombinant Proteins - metabolism; Redox reactions; Reductase; Science; Science (multidisciplinary); Spectroscopy; Spectrum Analysis; Substrates
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-10078-3

Hydride transfers play a crucial role in a multitude of biological redox reactions and are mediated by flavin, deazaflavin or nicotinamide adenine dinucleotide cofactors at standard redox potentials ranging from 0 to –340 mV. 2-Naphthoyl-CoA reductase, a key enzyme of oxygen-independent bacterial naphthalene degradation, uses a low-potential one-electron donor for the two-electron dearomatization of its substrate below the redox limit of known biological hydride transfer processes at E °’ = −493 mV. Here we demonstrate by X-ray structural analyses, QM/MM computational studies, and multiple spectroscopy/activity based titrations that highly cooperative electron transfer ( n  = 3) from a low-potential one-electron (FAD) to a two-electron (FMN) transferring flavin cofactor is the key to overcome the resonance stabilized aromatic system by hydride transfer in a highly hydrophobic pocket. The results evidence how the protein environment inversely functionalizes two flavins to switch from low-potential one-electron to hydride transfer at the thermodynamic limit of flavin redox chemistry. The reduction of 2-naphtoyl-CoA to 5,6 dihydro-2-naphtoyl-CoA by 2-naphtoyl-CoA reductase is below the negative redox limit usually encountered in biological hydride transfer. Here, via X-ray crystallography and spectroscopic analysis, the authors elucidated the mechanism behind this.