Site-Specific Oxidation State Assignments of the Iron Atoms in the [4Fe:4S] 2+/1+/0 States of the Nitrogenase Fe-Protein
- California Institute of Technology (CalTech), Pasadena, CA (United States). Division of Chemistry and Chemical Engineering
- California Institute of Technology (CalTech), Pasadena, CA (United States). Howard Hughes Medical Institute; California Institute of Technology (CalTech), Pasadena, CA (United States). Division of Chemistry and Chemical Engineering
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-c resolution structure for the ADP bound Fe-protein, the highest resolution Fe-protein structure presently determined. In the dithionitereduced [4Fe:4S]1+ state, our analysis identifies a solvent exposed, delocalized Fe2.5+ 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 to the nitrogenase molybdenum iron-protein. In the [4Fe:4S]0 and [4Fe:4S]2+ states, the SpReAD analysis supports oxidation states assignments for all irons in these clusters of Fe2+ and valence delocalized Fe2.5+ , respectively.
- Research Organization:
- SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities Division
- Grant/Contract Number:
- AC02-76SF00515
- OSTI ID:
- 1623488
- Journal Information:
- Angewandte Chemie (International Edition), Vol. 58, Issue 12; ISSN 1433-7851
- Publisher:
- WileyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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