NRVS Spectroscopy Resolves Distinct Bridging Hydride Intermediates in [NiFe]-Hydrogenase.

Area of Science:

• Biochemistry
• Spectroscopy
• Enzymology

Background:

• [NiFe]-hydrogenases are crucial enzymes for biological energy conversion.
• Understanding their catalytic mechanisms requires detailed characterization of reaction intermediates.
• The active site's iron atom plays a key role in catalysis.

Purpose of the Study:

• To probe the catalytic intermediates of H2-sensing [NiFe]-hydrogenase.
• To investigate the vibrational properties of metal-hydride species.
• To elucidate the structural dynamics of the [NiFe] center during catalysis.

Main Methods:

• Selective labeling of the active-site iron with 57Fe.
• Synchrotron-based nuclear resonance vibrational spectroscopy (NRVS).
• H/D isotope substitution and in situ hydride photolysis.

Main Results:

• Diagnostic metal-hydride vibrations were observed for Ni-C and Ni-SR intermediates.
• Distinct Fe-hydride vibrational bands indicate different bonding interactions.
• Conserved structural rigidity of the [NiFe] center was identified across catalytic species.

Conclusions:

• The study provides detailed insights into the vibrational spectra of key hydrogenase intermediates.
• Distinct metal-hydride interactions are present during the catalytic cycle.
• The structural rigidity of the [NiFe] center is essential for efficient electron transfer in [NiFe]-hydrogenases.