Direct Observation of an Iron-Bound Terminal Hydride in [FeFe]-Hydrogenase by Nuclear Resonance Vibrational Spectroscopy

• Published in: Journal of the American Chemical Society Vol. 139; no. 12; pp. 4306 - 4309
• Main Authors: Reijerse, Edward J, Pham, Cindy C, Pelmenschikov, Vladimir, Gilbert-Wilson, Ryan, Adamska-Venkatesh, Agnieszka, Siebel, Judith F, Gee, Leland B, Yoda, Yoshitaka, Tamasaku, Kenji, Lubitz, Wolfgang, Rauchfuss, Thomas B, Cramer, Stephen P
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 29-03-2017
• Subjects: Hydrogenase - chemistry; Hydrogenase - metabolism; Iron - chemistry; Iron - metabolism; Iron-Sulfur Proteins - chemistry; Iron-Sulfur Proteins - metabolism; Magnetic Resonance Spectroscopy; Molecular Conformation; Quantum Theory; Spectroscopy, Fourier Transform Infrared; Water - chemistry; Water - metabolism
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.7b00686

[FeFe]-hydrogenases catalyze the reversible reduction of protons to molecular hydrogen with extremely high efficiency. The active site (“H-cluster”) consists of a [4Fe–4S]H cluster linked through a bridging cysteine to a [2Fe]H subsite coordinated by CN– and CO ligands featuring a dithiol-amine moiety that serves as proton shuttle between the protein proton channel and the catalytic distal iron site (Fed). Although there is broad consensus that an iron-bound terminal hydride species must occur in the catalytic mechanism, such a species has never been directly observed experimentally. Here, we present FTIR and nuclear resonance vibrational spectroscopy (NRVS) experiments in conjunction with density functional theory (DFT) calculations on an [FeFe]-hydrogenase variant lacking the amine proton shuttle which is stabilizing a putative hydride state. The NRVS spectra unequivocally show the bending modes of the terminal Fe–H species fully consistent with widely accepted models of the catalytic cycle.