Conformational distribution in protein-bound [3Fe-4S]+ clusters : CW and pulsed EPR and 57Fe ENDOR of D. gigas hydrogenase

This paper discusses 9- and 35-GHz EPR spectra of the Desulfovibrio gigas [3Fe-4S] + cluster and also describes 35-GHz CW 57 Fe ENDOR measurements of isotopically enriched protein. The EPR spectra of [3Fe-4S] + clusters typically cannot be described by a well-defined g tensor. Their properties instead can be modeled with a formal treatment that assumes there is a distribution in the g values. This treatment implicitly assumes that the EPR spectra of such clusters are controlled by a distribution in protein conformation and cluster structure, but the validity of this assumption has never been confirmed by an experiment that correlates the EPR spectrum of a cluster with a microscopy cluster property