Low-barrier hydrogen bond powers long-range radical transfer in the metal-free ribonucleotide reductase
Abstract
Ribonucleotide reductases (RNRs) catalyze the conversion of ribonucleotide (RNA) to deoxyribonucleotide (DNA) building blocks initiated by a long-range (>30 Å) proton-coupled electron transfer (PCET) by mechanistic principles that remain much debated. By combining multiscale quantum and classical simulations with directed mutagenesis, X-ray crystallography, and vibrational and electron paramagnetic resonance spectroscopy, we elucidate here the molecular principles underlying how metal-free RNRs initiate the long-range PCET process by creating a highly stable 3,4-dihydroxyphenylalanine (DOPA) initiator radical. We show that DOPA• is redox-tuned by a low-barrier hydrogen bond (LBHB), with a delocalized proton that provides the catalytic power for the ribonucleotide reduction. We find that the LBHB couples to an extended hydrogen-bonded network, with distant mutations resulting in the loss of radical formation, and providing key molecular insight into the long-range radical transport mechanism in RNRs. On a general level, our findings support the direct involvement of LBHB in protein chemistry and the importance of quantum effects in enzyme catalysis.
Article Details
Journal Info
Proceedings of the National Academy of Sciences
National Academy of Sciences
Authors (13)
Abhishek Sirohiwal
Department of Inorganic and Physical Chemistry
Juliane John
Department of Biochemistry and Biophysics, Stockholm University, Arrhenius Laboratories for Natural Sciences
Yury Kutin
Department of Chemistry and Chemical Biology, Technical University Dortmund, Faculty for Chemistry and Chemical Biology
Rohit Kumar
Federico Baserga
Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin
Vivek Srinivas
Department of Biochemistry and Biophysics, Stockholm University, Arrhenius Laboratories for Natural Sciences
Hugo Lebrette
Laboratoire de Microbiologie et Génétique Moléculaires, Centre de Biologie Intégrative, CNRS, Université de Toulouse
Maximilian C. Pöverlein
Department of Biochemistry and Biophysics, Stockholm University, Arrhenius Laboratories for Natural Sciences
Ana P. Gamiz-Hernandez
Department of Biochemistry and Biophysics, Stockholm University, Arrhenius Laboratories for Natural Sciences
Joachim Heberle
Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin
Müge Kasanmascheff
Department of Chemistry and Chemical Biology, Technical University Dortmund, Faculty for Chemistry and Chemical Biology
Martin Högbom
Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences
Ville R. I. Kaila
Department of Biochemistry and Biophysics, Stockholm University, Svante Arrhenius väg 16C, Stockholm 10691, Sweden