Structural Evidence for Asymmetrical Nucleotide Interactions in Nitrogenase
The roles of ATP hydrolysis in electron-transfer (ET) reactions of the nitrogenase catalytic cycle remain obscure. Here, we present a new structure of a nitrogenase complex crystallized with MgADP and MgAMPPCP, an ATP analogue. In this structure the two nucleotides are bound asymmetrically by the Fe-protein subunits connected to the two different MoFe-protein subunits. This binding mode suggests that ATP hydrolysis and phosphate release may proceed by a stepwise mechanism. Through the associated Fe-protein conformational changes, a stepwise mechanism is anticipated to prolong the lifetime of the Fe-protein-MoFe-protein complex and, in turn, could orchestrate the sequence of intracomplex ET required for substrate reduction.
Additional Information© 2014 American Chemical Society. ACS AuthorChoice - This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes. Received: November 25, 2014, Published: December 18, 2014. This work was supported by NIH (GM099813 to F.A.T. and GM045162 to D.C.R.). F.A.T. acknowledges the Frasch Foundation for further support and the Moore Distinguished Scholar program at Caltech. We thank Mika Walton and Debarshi Mustafi for their contributions in the onset of this project, and the Gordon and Betty Moore Foundation for their support of the Molecular Observatory at Caltech. Operations at the Advanced Light Source are funded by the Office of Basic Energy Sciences of the DOE and NIH. Coordinates and structure factors have been deposited in the Protein Data Bank of the Research Collaboratory for Structural Bioinformatics, IDs 4WZA and 4WZB.
Published - ja511945e.pdf
Supplemental Material - ja511945e_si_001.pdf