Cysteine SH and Glutamate COOH Contributions to [NiFe] Hydrogenase Proton Transfer Revealed by Highly Sensitive FTIR Spectroscopy. (13th August 2019)

• Record Type: Journal Article
• Authors: Tai, Hulin; Nishikawa, Koji; Higuchi, Yoshiki; Mao, Zong‐wan; Hirota, Shun
• Is Part Of: Angewandte Chemie. Volume 131:Number 38(2019)
• Page Start: 13419
• Page End: 13424
• Publication Date: 2019-08-13
• Subjects: Biokatalyse -- Hydrogenase -- IR-Spektroskopie -- Protonentransfer -- Wasserstoff; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.201904472
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: A [NiFe] hydrogenase (H2 ase) is a proton‐coupled electron transfer enzyme that catalyses reversible H2 oxidation; however, its fundamental proton transfer pathway remains unknown. Herein, we observed the protonation of Cys546‐SH and Glu34‐COOH near the Ni–Fe site with high‐sensitivity infrared difference spectra by utilizing Ni‐C‐to‐Ni‐L and Ni‐C‐to‐Ni‐SIa photoconversions. Protonated Cys546‐SH in the Ni‐L state was verified by the observed SH stretching frequency (2505 cm −1 ), whereas Cys546 was deprotonated in the Ni‐C and Ni‐SIa states. Glu34‐COOH was double H‐bonded in the Ni‐L state, as determined by the COOH stretching frequency (1700 cm −1 ), and single H‐bonded in the Ni‐C and Ni‐SIa states. Additionally, a stretching mode of an ordered water molecule was observed in the Ni‐L and Ni‐C states. These results elucidate the organized proton transfer pathway during the catalytic reaction of a [NiFe] H2 ase, which is regulated by the H‐bond network of Cys546, Glu34, and an ordered water molecule. Abstract : Brücken zum Erfolg : Protoniertes Cys546‐SH, wasserstoffbrückengebundenes Glu34‐COOH und Frequenzen von geordnetem Wasser wurden für die Ni‐C‐, Ni‐L‐ und Ni‐SIa ‐Zustände der [NiFe]‐Hydrogenase beobachtet. Das zeigt, dass der Pfad des organisierten Protonentransfers in der katalytischen Reaktion durch das Wasserstoffbrückennetzwerk von Cys546, Glu34 und geordneten Wassermolekülen reguliert wird.