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Title: Exploring Electron/Proton Transfer and Conformational Changes in the Nitrogenase MoFe Protein and FeMo-cofactor Through Cryoreduction/EPR Measurements

Authors:
 [1];  [2];  [2];  [2];  [1];  [3];  [2];  [1]
  1. Department of Chemistry, Northwestern University, Evanston IL 60208 USA
  2. Department of Chemistry and Biochemistry, Utah State University, Logan UT 84322 USA
  3. Department of Biochemistry, Virginia Tech, 110 Fralin Hall Blacksburg VA 24061 USA
Publication Date:
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1401224
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Israel Journal of Chemistry
Additional Journal Information:
Journal Volume: 56; Journal Issue: 9-10; Related Information: CHORUS Timestamp: 2017-10-20 16:29:05; Journal ID: ISSN 0021-2148
Publisher:
Wiley Blackwell (John Wiley & Sons)
Country of Publication:
Israel
Language:
English

Citation Formats

Davydov, Roman, Khadka, Nimesh, Yang, Zhi-Yong, Fielding, Andrew J., Lukoyanov, Dmitriy, Dean, Dennis R., Seefeldt, Lance C., and Hoffman, Brian M.. Exploring Electron/Proton Transfer and Conformational Changes in the Nitrogenase MoFe Protein and FeMo-cofactor Through Cryoreduction/EPR Measurements. Israel: N. p., 2016. Web. doi:10.1002/ijch.201600026.
Davydov, Roman, Khadka, Nimesh, Yang, Zhi-Yong, Fielding, Andrew J., Lukoyanov, Dmitriy, Dean, Dennis R., Seefeldt, Lance C., & Hoffman, Brian M.. Exploring Electron/Proton Transfer and Conformational Changes in the Nitrogenase MoFe Protein and FeMo-cofactor Through Cryoreduction/EPR Measurements. Israel. doi:10.1002/ijch.201600026.
Davydov, Roman, Khadka, Nimesh, Yang, Zhi-Yong, Fielding, Andrew J., Lukoyanov, Dmitriy, Dean, Dennis R., Seefeldt, Lance C., and Hoffman, Brian M.. 2016. "Exploring Electron/Proton Transfer and Conformational Changes in the Nitrogenase MoFe Protein and FeMo-cofactor Through Cryoreduction/EPR Measurements". Israel. doi:10.1002/ijch.201600026.
@article{osti_1401224,
title = {Exploring Electron/Proton Transfer and Conformational Changes in the Nitrogenase MoFe Protein and FeMo-cofactor Through Cryoreduction/EPR Measurements},
author = {Davydov, Roman and Khadka, Nimesh and Yang, Zhi-Yong and Fielding, Andrew J. and Lukoyanov, Dmitriy and Dean, Dennis R. and Seefeldt, Lance C. and Hoffman, Brian M.},
abstractNote = {},
doi = {10.1002/ijch.201600026},
journal = {Israel Journal of Chemistry},
number = 9-10,
volume = 56,
place = {Israel},
year = 2016,
month = 7
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1002/ijch.201600026

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  • The biological reduction of dinitrogen to ammonia by the nitrogenase system requires the MoFe protein, which contains two iron-molybdenum cofactors (FeMoco) and two Fe-S P-clusters, and the Fe protein, which is the electron donor in catalysis. We report herein a new series of Mo-K edge EXAFS studies of highly concentrated isolated FeMoco, isolated FeMoco plus CN-and the MoFe protein. Very high quality data has been obtained over a wide k-range through improved experimental techniques. In addition, new EXAFS analysis methodology (called GNXAS) based on multiple scattering formalism with further enhancements has been used to analyze the data. Several important resultsmore » have emerged: for the first time a second shell of Fe atoms at [approximately] 5.1 [angstrom] from the Mo is clearly present in the EXAFS for both FeMoco and the MoFe protein. This provides direct evidence for the [open quotes]intact[close quotes] nature of extracted FeMoco and demonstrates the ability to detect and analyze such long-range absorber-scatter interactions. Second, the EXAFS results give very accurate metrical details of the FeMoco sites, and these differ from those of FeMoco from the X-ray crystal structure of the MoFe protein at its current level of refinement. Finally, using the GNXAS analysis method, it is shown that added CN[sup [minus]] coordinates to Mo in isolated FeMoco. 35 refs., 6 figs.« less
  • Nitrogenase is a complex bacterial enzyme system that is responsible for the conversion of atmospheric N/sub 2/ to ammonia. The structure and function of molybdenum in the MoFe protein of this system has been the subject of a number of investigations, including the use of X-ray absorption spectroscopy. This paper reports the results of the authors recent studies on several states of the MoFe protein and its FeMo cofactor (which is extruded by treatment with N-methylformamide). Mo K-edge (XANES) and extended fine structure (EXAFS) spectra have been recorded to high energies above the absorption edge with excellent signal-to-nose on themore » semireduced form of the MoFe protein from both Clostridium pasteurianum and Azotobacter vinelandii and on the as isolated FeMo-co and FeMo-co treated with benzenethiol and with benzeneselenol. In all of the states studied, EXAFS results reveal that the Mo is in an environment that contains two or three oxygen (or nitrogen) atoms at 2.10-2.12 A, three to five S atoms at 2.37 A, and three to four Fe atoms at 2.68-2.70 A. The numbers of these ligands change upon removal of the cofactor from the protein as discussed in the paper. For FeMo-co, comparisons also show that thil/selenol is not binding directly to the Mo site. The results of these EXAFS (and their XANES published earlier) definitely show the presence of several low-Z ligands and are not compatible with a tetrahedral arrangement of only nearest S neighbors at the Mo site.« less