Maturation of nitrogenase cofactor—the role of a class E radical SAM methyltransferase NifB

• Published in: Current opinion in chemical biology Vol. 31; pp. 188 - 194
• Main Authors: Hu, Yilin, Ribbe, Markus W
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.04.2016
• Subjects: Amino Acid Sequence; Crystallography; Methyltransferases - chemistry; Methyltransferases - metabolism; Nitrogenase - metabolism; S-Adenosylmethionine - metabolism; Sequence Homology, Amino Acid
• ISSN: 1367-5931; 1879-0402
• DOI: 10.1016/j.cbpa.2016.02.016

•The carbide of nitrogense M-cluster originates from the methyl group of SAM.•The insertion of carbide is catalyzed by NifB via a radical SAM-dependent mechanism.•The methyl group is transferred from SAM to an sulfur atom of the M-cluster precursor.•The transfer of methyl to the M-cluster precursor occurs before hydrogen abstraction.•The NifB protein family represents as a new class of radical SAM methyltransferases. Nitrogenase catalyzes the important reactions of N2-reduction, CO-reduction and CO2-reduction at its active cofactor site. Designated the M-cluster, this complex metallocofactor is assembled through the generation of a characteristic 8Fe-core before the insertion of Mo and homocitrate that completes the stoichiometry of the M-cluster. NifB catalyzes the crucial step of radical SAM-dependent carbide insertion that occurs concomitant with the insertion a ‘9th’ sulfur and the rearrangement/coupling of two 4Fe-clusters into a complete 8Fe-core of the M-cluster. Further categorization of a family of NifB proteins as a new class of radical SAM methyltransferases suggests a general function of these proteins in complex metallocofactor assembly and provides a new platform for unveiling unprecedented chemical reactions catalyzed by biological systems.