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          Institute: MPI für bioanorganische Chemie     Collection: MPI für bioanorganische Chemie     Display Documents

ID: 734275.0, MPI für bioanorganische Chemie / MPI für bioanorganische Chemie
Proton Coupled Electronic Rearrangement within the H-Cluster as an Essential Step in the Catalytic Cycle of [FeFe] Hydrogenases
Authors:Sommer, Constanze; Adamska-Venkatesh, Agnieszka; Pawlak, Krzysztof; Birrell, James A.; Rüdiger, Olaf; Reijerse, Edward J.; Lubitz, Wolfgang
Date of Publication (YYYY-MM-DD):2017
Title of Journal:Journal of the American Chemical Society
Journal Abbrev.:J.Am.Chem.Soc.
Issue / Number:4
Start Page:1440
End Page:1443
Review Status:Internal review
Audience:Experts Only
Abstract / Description:The active site of [FeFe] hydrogenases, the H-cluster, consists of a [4Fe-4S] cluster connected via a bridging cysteine to a [2Fe] complex carrying CO and CN- ligands as well as a bridging aza-dithiolate ligand (ADT) of which the amine moiety serves as a proton shuttle between the protein and the H-cluster. During the catalytic cycle, the two subclusters change oxidation states: [4Fe-4S](2+)(H) double left right arrow [4Fe-4S](+)(H) and [Fe(I)Fe(II)](H) double left right arrow [Fe(I)Fe(I)]-(H) thereby enabling the storage of the two electrons needed for the catalyzed reaction 2(H+) + 2e(-) reversible arrow H-2 center dot. Using FTIR spectro-electrochemistry on the [FeFe] hydrogenase from Chlamydomonas reinhardtii (CrHydA1) at different pH values, we resolve the redox and protonation events in the catalytic cycle and determine their intrinsic thermodynamic parameters. We show that the singly reduced state H-red of the H-cluster actually consists of two species: H-red = [4Fe-4S](+)(H) [Fe(I)Fe(ll)](H) and HredH+ = [4Fe-4S](2+)(H) [Fe(I)Fe(I)](H) (H+) related by proton coupled electronic rearrangement. The two redox events in the catalytic cycle occur on the [4Fe-4S](H) subcluster at similar midpoint -potentials (-375 vs 418 mV); the protonation event (H-red/H(red)H(+)1) has a pK(a) approximate to 7.2.
Comment of the Author/Creator:Date: 2017, FEB 1 2017
External Publication Status:published
Document Type:Article
Version Comment:Automatic journal name synchronization
Communicated by:N. N.
Affiliations:MPI für bioanorganische Chemie
Identifiers:ISI:000393355600023 [ID No:1]
ISSN:0002-7863 [ID No:2]
DOI:10.1021/jacs.6b12636 [ID No:3]
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