The interstitial atom of the nitrogenase FeMo-cofactor: ENDOR and ESEEM evidence that it is not a nitrogen.
X-ray crystallographic study of the nitrogenase MoFe protein revealed electron density from an atom (denoted X) inside the active-site metal cluster, the [MoFe7S9:homocitrate] FeMo-cofactor. The electron density associated with X is consistent with a single N, O, or C atom. We now have tested whether X is an N or not by comparing the Q-band ENDOR and ESEEM signals from resting-state (S = 3/2) MoFe protein and NMF-extracted FeMo-co from bacteria grown with either 14N or 15N as the exclusive N source. All of the 14N or 15N signals associated with the protein are lost upon extraction of the FeMo-co. We interpret this as strong evidence that X is not an N.
Yang
Tran-Chin
TC
Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA.
Maeser
Nathan K
NK
Laryukhin
Mikhail
M
Lee
Hong-In
HI
Dean
Dennis R
DR
Seefeldt
Lance C
LC
Hoffman
Brian M
BM
D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D008958:Models, Molecular; D008983:Molybdoferredoxin / Q000737:chemistry*; D009591:Nitrogenase / Q000737:chemistry*
D008983:Molybdoferredoxin; D009591:Nitrogenase