How Nitrogenase Shakes – Initial Information about P-Cluster and FeMo-cofactor Normal Modes from Nuclear Resonance Vibrational Spectroscopy (NRVS)

摘要

Nitrogenase catalyzes a reaction critical for life, the reduction of N2 to NH3, yet we still know relatively little about its catalytic mechanism. We have used the synchrotron technique of ⁵⁷Fe nuclear resonance vibrational spectroscopy (NRVS) to study the dynamics of the Fe-S clusters in this enzyme. The catalytic site FeMo-cofactor exhibits a strong signal near 190 cm⁻¹, where conventional Fe-S clusters have weak NRVS. This intensity is ascribed to cluster breathing modes whose frequency is raised by an interstitial atom. A variety of Fe-S stretching modes are also observed between 250 and 400 cm⁻¹. This work is the first spectroscopic information about the vibrational modes of the intact nitrogenase FeMo-cofactor and P-cluster.