Vibrational Perturbation of the [FeFe] Hydrogenase H‑Cluster Revealed by 13C2H‑ADT Labeling
dataset
posted on 2021-05-27, 20:15 authored by Vladimir Pelmenschikov, James A. Birrell, Leland B. Gee, Casseday P. Richers, Edward J. Reijerse, Hongxin Wang, Simon Arragain, Nakul Mishra, Yoshitaka Yoda, Hiroaki Matsuura, Lei Li, Kenji Tamasaku, Thomas B. Rauchfuss, Wolfgang Lubitz, Stephen P. Cramer[FeFe]
hydrogenases are highly active catalysts for the interconversion
of molecular hydrogen with protons and electrons. Here, we use a combination
of isotopic labeling, 57Fe nuclear resonance vibrational spectroscopy (NRVS),
and density functional theory (DFT) calculations to observe and characterize
the vibrational modes involving motion of the 2-azapropane-1,3-dithiolate
(ADT) ligand bridging the two iron sites in the [2Fe]H subcluster.
A −13C2H2– ADT labeling
in the synthetic diiron precursor of [2Fe]H produced isotope
effects observed throughout the NRVS spectrum. The two precursor isotopologues
were then used to reconstitute the H-cluster of [FeFe] hydrogenase
from Chlamydomonas reinhardtii (CrHydA1), and NRVS was measured on samples poised in the catalytically
crucial Hhyd state containing a terminal hydride at the
distal Fe site. The 13C2H isotope effects were
observed also in the Hhyd spectrum. DFT simulations of
the spectra allowed identification of the 57Fe normal modes
coupled to the ADT ligand motions. Particularly, a variety of normal
modes involve shortening of the distance between the distal Fe–H
hydride and ADT N–H bridgehead hydrogen, which may be relevant
to the formation of a transition state on the way to H2 formation.
