6YF4

[FeFe]-hydrogenase I from Clostridium pasteurianum (CpI), variant E279D

Summary for 6YF4

• Entry DOI: 10.2210/pdb6yf4/pdb
• Related: 4XDC
• Descriptor: Iron hydrogenase 1, dicarbonyl[bis(cyanide-kappaC)]-mu-(iminodimethanethiolatato-1kappaS:2kappaS)-mu-(oxomethylidene)diiron(2+), IRON/SULFUR CLUSTER, ... (6 entities in total)
• Functional Keywords: [fefe]-hydrogenase, clostridium pasteurianum, e279d, oxidoreductase
• Biological source: Clostridium pasteurianum
• Total number of polymer chains: 2
• Total formula weight: 134142.34

Authors

Duan, J.,Hofmann, E.,Happe, T. (deposition date: 2020-03-25, release date: 2020-09-02, Last modification date: 2024-01-24)

Primary citation

Lampret, O.,Duan, J.,Hofmann, E.,Winkler, M.,Armstrong, F.A.,Happe, T.
The roles of long-range proton-coupled electron transfer in the directionality and efficiency of [FeFe]-hydrogenases.
Proc.Natl.Acad.Sci.USA, 117:20520-20529, 2020

PubMed Abstract: As paradigms for proton-coupled electron transfer in enzymes and benchmarks for a fully renewable H technology, [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 from (CpI) and (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/H thermodynamic potential, clearly signaling a departure from electrocatalytic reversibility as electron and proton transfers begin to be decoupled.

PubMed: 32796105
DOI: 10.1073/pnas.2007090117

Experimental method

X-RAY DIFFRACTION (1.77 Å)