Intermediates trapped during nitrogenase reduction of N≡N, CH 3-N=NH, and H2N-NH2

Brett M. Barney, Tran Chin Yang, Robert Y. Igarashi, Patricia C. Dos Santos, Mikhail Laryukhin, Hong In Lee, Brian M. Hoffman, Dennis R. Dean, Lance C. Seefeldt

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99 Scopus citations

Abstract

A high population intermediate has been trapped on the nitrogenase active site FeMo cofactor during reduction of N2. In addition, intermediates have been trapped during reduction of CH3-N=NH by the α-195Gln variant and during reduction of H2N-NH2 by the α-70Ala/α-195Gln variant. Each of these trapped states shows an EPR signal arising from an S = 1/2 state of the FeMo cofactor. 15N ENDOR shows that each intermediate has a nitrogenous species bound to the FeMo cofactor, with a single type of N seen for each bound intermediate. The g tensors are unique to each intermediate, g(e) = [2.084, 1.993, 1.969], g(m) = [2.083, 2.021, 1.993], g(l) = [2.082, 2.015, 1.987], as are the 15N hyperfine couplings at g1, which suggests that three distinct stages of NN reduction may have been trapped. The 1H ENDOR spectra show that the N2 intermediate is at a distinct and earlier stage of reduction from the other two, so at least two stages of NN reduction have been trapped. Some possible structures of the hydrazine intermediate are presented.

Original languageEnglish (US)
Pages (from-to)14960-14961
Number of pages2
JournalJournal of the American Chemical Society
Volume127
Issue number43
DOIs
StatePublished - Nov 2 2005

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