Proton-Coupled Electron Transfer Drives Long-Range Proton Translocation in Bioinspired Systems

2019 ◽  
Vol 141 (36) ◽  
pp. 14057-14061 ◽  
Author(s):  
Emmanuel Odella ◽  
Brian L. Wadsworth ◽  
S. Jimena Mora ◽  
Joshua J. Goings ◽  
Mioy T. Huynh ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Long Range ◽  
Proton Translocation ◽  
Proton Coupled Electron Transfer

Radical Initiation in the Class I Ribonucleotide Reductase: Long-Range Proton-Coupled Electron Transfer?

ChemInform ◽  
2003 ◽  
Vol 34 (32) ◽  
Author(s):  
JoAnne Stubbe ◽  
Daniel G. Nocera ◽  
Cyril S. Yee ◽  
Michelle C. Y. Chang
Keyword(s):  
Electron Transfer ◽  
Long Range ◽  
Ribonucleotide Reductase ◽  
Class I ◽  
Radical Initiation ◽  
Proton Coupled Electron Transfer

Long-range proton-coupled electron transfer in the Escherichia coli class Ia ribonucleotide reductase

2017 ◽  
Vol 61 (2) ◽  
pp. 281-292 ◽  
Author(s):  
Steven Y. Reece ◽  
Mohammad R. Seyedsayamdost
Keyword(s):  
Escherichia Coli ◽  
Electron Transfer ◽  
Amino Acid ◽  
Long Range ◽  
Ribonucleotide Reductase ◽  
Unnatural Amino Acids ◽  
Radical Mechanism ◽  
Tyrosyl Radical ◽  
Proton Coupled Electron Transfer ◽  
Vis Spectroscopy

Escherichia coli class Ia ribonucleotide reductase (RNR) catalyzes the conversion of nucleotides to 2′-deoxynucleotides using a radical mechanism. Each turnover requires radical transfer from an assembled diferric tyrosyl radical (Y•) cofactor to the enzyme active site over 35 Å away. This unprecedented reaction occurs via an amino acid radical hopping pathway spanning two protein subunits. To study the mechanism of radical transport in RNR, a suite of biochemical approaches have been developed, such as site-directed incorporation of unnatural amino acids with altered electronic properties and photochemical generation of radical intermediates. The resulting variant RNRs have been investigated using a variety of time-resolved physical techniques, including transient absorption and stopped-flow UV-Vis spectroscopy, as well as rapid freeze-quench EPR, ENDOR, and PELDOR spectroscopic methods. The data suggest that radical transport occurs via proton-coupled electron transfer (PCET) and that the protein structure has evolved to manage the proton and electron transfer co-ordinates in order to prevent ‘off-pathway’ reactivity and build-up of oxidised intermediates. Thus, precise design and control over the factors that govern PCET is key to enabling reversible and long-range charge transport by amino acid radicals in RNR.

scholarly journals Long-Range Proton-Coupled Electron-Transfer Reactions of Bis(imidazole) Iron Tetraphenylporphyrins Linked to Benzoates

2013 ◽  
Vol 4 (3) ◽  
pp. 519-523 ◽  
Author(s):  
Jeffrey J. Warren ◽  
Artur R. Menzeleev ◽  
Joshua S. Kretchmer ◽  
Thomas F. Miller ◽  
Harry B. Gray ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Long Range ◽  
Transfer Reactions ◽  
Electron Transfer Reactions ◽  
Proton Coupled Electron Transfer

2,3-Difluorotyrosine at Position 356 of Ribonucleotide Reductase R2:  A Probe of Long-Range Proton-Coupled Electron Transfer

2003 ◽  
Vol 125 (35) ◽  
pp. 10506-10507 ◽  
Author(s):  
Cyril S. Yee ◽  
Chang ◽  
Jie Ge ◽  
Daniel G. Nocera ◽  
JoAnne Stubbe
Keyword(s):  
Electron Transfer ◽  
Long Range ◽  
Ribonucleotide Reductase ◽  
Proton Coupled Electron Transfer ◽  
Ribonucleotide Reductase R2

scholarly journals The roles of long-range proton-coupled electron transfer in the directionality and efficiency of [FeFe]-hydrogenases

2020 ◽  
Vol 117 (34) ◽  
pp. 20520-20529 ◽  
Author(s):  
Oliver Lampret ◽  
Jifu Duan ◽  
Eckhard Hofmann ◽  
Martin Winkler ◽  
Fraser A. Armstrong ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Proton Transfer ◽  
Long Range ◽  
Turnover Rate ◽  
Hydrogen Oxidation ◽  
Significant Activity ◽  
Catalytic Current ◽  
Protein Film ◽  
Proton Coupled Electron Transfer ◽  
Wide Range

As paradigms for proton-coupled electron transfer in enzymes and benchmarks for a fully renewable H2technology, [FeFe]-hydrogenases behave as highly reversible electrocatalysts when immobilized on an electrode, operating in both catalytic directions with minimal overpotential requirement. Using the [FeFe]-hydrogenases fromClostridium pasteurianum(CpI) andChlamydomonas reinhardtii(CrHydA1) we have conducted site-directed mutagenesis and protein film electrochemistry to determine how efficient catalysis depends on the long-range coupling of electron and proton transfer steps. Importantly, the electron and proton transfer pathways in [FeFe]-hydrogenases are well separated from each other in space. Variants with conservative substitutions (glutamate to aspartate) in either of two positions in the proton-transfer pathway retain significant activity and reveal the consequences of slowing down proton transfer for both catalytic directions over a wide range of pH and potential values. Proton reduction in the variants is impaired mainly by limiting the turnover rate, which drops sharply as the pH is raised, showing that proton capture from bulk solvent becomes critical. In contrast, hydrogen oxidation is affected in two ways: by limiting the turnover rate and by a large overpotential requirement that increases as the pH is raised, consistent with the accumulation of a reduced and protonated intermediate. A unique observation having fundamental significance is made under conditions where the variants still retain sufficient catalytic activity in both directions: An inflection appears as the catalytic current switches direction at the 2H+/H2thermodynamic potential, clearly signaling a departure from electrocatalytic reversibility as electron and proton transfers begin to be decoupled.

Sign in / Sign up

Export Citation Format

Share Document