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Title: Identification of a catalytic iron-hydride at the H-cluster of [FeFe]-hydrogenase

Hydrogenases couple electrochemical potential to the reversible chemical transformation of H 2 and protons, yet the reaction mechanism and composition of intermediates are not fully understood. In this Communication we describe the biophysical properties of a hydride-bound state (H hyd) of the [FeFe]-hydrogenase from Chlamydomonas reinhardtii. The catalytic H-cluster of [FeFe]-hydrogenase consists of a [4Fe-4S] subcluster ([4Fe-4S] H) linked by a cysteine thiol to an azadithiolate-bridged 2Fe subcluster ([2Fe] H) with CO and CN- ligands. Mossbauer analysis and density functional theory (DFT) calculations show that H hyd consists of a reduced [4Fe-4S] H + coupled to a diferrous [2Fe] H with a terminally bound Fe-hydride. The existence of the Fe-hydride in Hhyd was demonstrated by an unusually low Mossbauer isomer shift of the distal Fe of the [2Fe] H subcluster. As a result, a DFT model of H hyd shows that the Fe-hydride is part of a H-bonding network with the nearby bridging azadithiolate to facilitate fast proton exchange and catalytic turnover.
Authors:
 [1] ; ORCiD logo [2] ;  [1] ; ORCiD logo [1]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  2. Carnegie Mellon Univ., Pittsburgh, PA (United States)
Publication Date:
Report Number(s):
NREL/JA-2700-67578
Journal ID: ISSN 0002-7863
Grant/Contract Number:
AC36-08GO28308
Type:
Accepted Manuscript
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 139; Journal Issue: 1; Journal ID: ISSN 0002-7863
Publisher:
American Chemical Society (ACS)
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Chlamydomonas reinhardtii; [FeFe]-hydrogenase; electrochemical potential
OSTI Identifier:
1340645