ja6b03329_si_001.pdf (218.72 kB)
Electron Paramagnetic Resonance Characterization of Three Iron–Sulfur Clusters Present in the Nitrogenase Cofactor Maturase NifB from Methanocaldococcus infernus
journal contribution
posted on 2016-06-06, 00:00 authored by Jarett Wilcoxen, Simon Arragain, Alessandro A. Scandurra, Emilio Jimenez-Vicente, Carlos Echavarri-Erasun, Stephan Pollmann, R. David Britt, Luis M. RubioNifB
utilizes two equivalents of S-adenosyl methionine
(SAM) to insert a carbide atom and fuse two substrate [Fe–S]
clusters forming the NifB cofactor (NifB-co), which is then passed
to NifEN for further modification to form the iron–molybdenum
cofactor (FeMo-co) of nitrogenase. Here, we demonstrate that NifB
from the methanogen Methanocaldococcus infernus is
a radical SAM enzyme able to reductively cleave SAM to 5′-deoxyadenosine
radical and is competent in FeMo-co maturation. Using electron paramagnetic
resonance spectroscopy we have characterized three [4Fe–4S]
clusters, one SAM binding cluster, and two auxiliary clusters probably
acting as substrates for NifB-co formation. Nitrogen coordination
to one or more of the auxiliary clusters in NifB was observed, and
its mechanistic implications for NifB-co dissociation from the maturase
are discussed.