Premium
X‐Ray Crystallographic Analysis of NifB with a Full Complement of Clusters: Structural Insights into the Radical SAM‐Dependent Carbide Insertion During Nitrogenase Cofactor Assembly
Author(s) -
Kang Wonchull,
Rettberg Lee A.,
Stiebritz Martin T.,
Jasniewski Andrew J.,
Tanifuji Kazuki,
Lee Chi Chung,
Ribbe Markus W.,
Hu Yilin
Publication year - 2021
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.202011367
Subject(s) - cofactor , nitrogenase , chemistry , stereochemistry , crystallography , biosynthesis , enzyme , biochemistry , organic chemistry , nitrogen fixation , nitrogen
NifB is an essential radical SAM enzyme required for the assembly of an 8Fe core of the nitrogenase cofactor. Herein, we report the X‐ray crystal structures of Methanobacterium thermoautotrophicum NifB without (apo Mt NifB) and with (holo Mt NifB) a full complement of three [Fe 4 S 4 ] clusters. Both apo and holo Mt NifB contain a partial TIM barrel core, but unlike apo Mt NifB, holo Mt NifB is fully assembled and competent in cofactor biosynthesis. The radical SAM (RS)‐cluster is coordinated by three Cys, and the adjacent K1‐ and K2‐clusters, representing the precursor to an 8Fe cofactor core, are each coordinated by one His and two Cys. Prediction of substrate channels, combined with in silico docking of SAM in holo Mt NifB, suggests the binding of SAM between the RS‐ and K2‐clusters and putative paths for entry of SAM and exit of products of SAM cleavage, thereby providing important mechanistic insights into the radical SAM‐dependent carbide insertion concomitant with cofactor core formation.