Séminaire IBS : From Catalysis to Sensing : Proton Transfer in [FeFe]-hydrogenases

Par Dr Moritz Senger (Université d’Uppsala, Département de chimie pour les sciences de la vie, Biochimie, Suède)

Enzymes are natures catalysts enabling challenging reactions at ambient conditions and at low overpotentials. In particular, [FeFe]-hydrogenases which catalyse bidirectional H2 turnover (2e- + 2H+ <-> H2) at high turnover numbers raise interest for their application in a green hydrogen economy. In [FeFe]-hydrogenases catalysis takes place at a unique diiron cofactor that is equipped with carbon monoxide (CO) and cyanide (CN) ligands. They serve as intrinsic infrared active probes sensitive to redox changes located directly at the centre of the catalytic reaction. This in isolation inactive di-iron cofactor becomes efficient H2 catalyst when incorporated into the [FeFe]-hydrogenase protein scaffold. More recently H2 sensing [FeFe]-hydrogenases have been characterised using the identical cofactor but for H2 sensing. The fundamental design principles of the protein scaffolds to selectively tune cofactor function either to efficient H2 catalyst or to H2 sensor remain unknown.
Here we use organic dyes to artificially activate catalytic [1-2] and sensory [3-5] [FeFe]-hydrogenases photochemically and investigate them via in situ ATR-FTIR spectroscopy. Following changes of the cofactor CO and CN ligands, single carboxylic acid residues and collective amide I modes, we show that protein scaffold differences are not limited to the cofactor second coordination sphere but extend through the whole protein via proton transfer pathways, secondary structure changes and most likely dimerization events. More general, our results give a first idea how protein scaffolds can tune cofactor functions.