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Spectroscopic Characterization of an Eight‐Iron Nitrogenase Cofactor Precursor that Lacks the “9 th Sulfur”
Author(s) -
Jasniewski Andrew J.,
Wilcoxen Jarett,
Tanifuji Kazuki,
Hedman Britt,
Hodgson Keith O.,
Britt R. David,
Hu Yilin,
Ribbe Markus W.
Publication year - 2019
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201907593
Subject(s) - nitrogenase , cofactor , sulfur , cluster (spacecraft) , iron–sulfur cluster , chemistry , stereochemistry , crystallography , biochemistry , enzyme , nitrogen fixation , organic chemistry , computer science , nitrogen , programming language
Nitrogenases catalyze the reduction of N 2 to NH 4 + at its cofactor site. Designated the M‐cluster, this [MoFe 7 S 9 C( R ‐homocitrate)] cofactor is synthesized via the transformation of a [Fe 4 S 4 ] cluster pair into an [Fe 8 S 9 C] precursor (designated the L‐cluster) prior to insertion of Mo and homocitrate. We report the characterization of an eight‐iron cofactor precursor (designated the L*‐cluster), which is proposed to have the composition [Fe 8 S 8 C] and lack the “9 th sulfur” in the belt region of the L‐cluster. Our X‐ray absorption and electron spin echo envelope modulation (ESEEM) analyses strongly suggest that the L*‐cluster represents a structural homologue to the l ‐cluster except for the missing belt sulfur. The absence of a belt sulfur from the L*‐cluster may prove beneficial for labeling the catalytically important belt region, which could in turn facilitate investigations into the reaction mechanism of nitrogenases.