Structural Characterization of Four Redox States of the P-cluster in Molybdenum Nitrogenase via Electrochemical Control of Crystals.

Shoba Laxmi, William K Myers, Zhi-Yong Yang, Lance C Seefeldt, Stephen B Carr, Kylie A Vincent

Journal: Journal of the American Chemical Society 2026;148(35):37583-37588

PMID: 42714517

Abstract

We report X-ray crystallographic structures of the Azotobacter vinelandii nitrogenase MoFe protein showing the 8Fe-7S electron-transfer P-cluster in four redox states. Using electrochemical poising of protein crystals, together with in crystallo EPR spectroscopic verification of the redox state, we obtain structures showing the P-cluster at PN, P1+, P2+, and P3+ levels. This provides a detailed structural characterization of P-cluster rearrangement between the catalytically relevant PN and P1+ levels and the first experimental confirmation that the S = 7/2 P3+ state is structurally similar to P2+. These studies pave the way for future understanding of the structure-function relationship in nitrogenase catalysis.

Address: Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, OxfordOX1 3QR, U.K.; Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus, DidcotOX11 0QX, U.K.; Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, OxfordOX1 3QR, U.K.; Centre for Advanced Electron Spin Resonance (CAESR), University of Oxford, OxfordOX1 3QR, U.K.; Department of Chemistry and Biochemistry, Utah State University, Logan, Utah84322, United States.; Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, OxfordOX1 3QR, U.K.

DOI: 10.1021/jacs.6c08522

MeSH Terms: Oxidation-Reduction, Azotobacter vinelandii, Nitrogenase, Crystallography, X-Ray, Models, Molecular, Molybdenum, Molybdoferredoxin, Electrochemical Techniques