Site-Specific Oxidation State Assignments of the Iron Atoms in the [4Fe:4S]^2+/1+/0 States of the Nitrogenase Fe-Protein.

ABSTRACT: The nitrogenase iron protein (Fe-protein) contains an unusual [4Fe:4S] iron-sulphur cluster that is stable in three oxidation states: 2+, 1+, and 0. Here, we use spatially resolved anomalous dispersion (SpReAD) refinement to determine oxidation assignments for the individual irons for each state. Additionally, we report the 1.13-Å resolution structure for the ADP bound Fe-protein, the highest resolution Fe-protein structure presently determined. In the dithionite-reduced [4Fe:4S]¹⁺ state, our analysis identifies a solvent exposed, delocalized Fe^2.5+ pair and a buried Fe²⁺ pair. We propose that ATP binding by the Fe-protein promotes an internal redox rearrangement such that the solvent-exposed Fe pair becomes reduced, thereby facilitating electron transfer t

SUBMITTER: Wenke BB 

PROVIDER: S-EPMC6519357 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature