7jmb

Publication Abstract from PubMed

NifB is an essential radical SAM enzyme for the assembly of an 8Fe core of the nitrogenase cofactor. Here we report the crystal structures of Methanobacterium thermoautotrophicum NifB without (apo Mt NifB) and with (holo Mt NifB) a full complement of three [Fe4S4] clusters. Both apo and holo Mt NifB contain a partial TIM barrel core; yet, unlike apo Mt NifB that is structurally disordered outside the TIM barrel, holo Mt NifB is fully assembled and competent in cofactor biosynthesis. Of the three [Fe4S4] clusters in holo Mt NifB, the canonical radical SAM (RS)-cluster, like those in other radical SAM enzymes, is coordinated by three Cys ligands; whereas the adjacently positioned K1- and K2-clusters, representing the precursor to an 8Fe cofactor core, are each coordinated by one His and two Cys ligands. Prediction of substrate channels, combined with in silico docking of SAM in holo Mt NifB, suggests plausible 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.

Crystallographic analysis of NifB with a full complement of clusters: Structural insights into the radical SAM-dependent carbide insertion during nitrogenase cofactor assembly.,Kang W, Rettberg L, Stiebritz M, Jasniewski A, Tanifuji K, Lee CC, Ribbe MW, Hu Y Angew Chem Int Ed Engl. 2020 Oct 9. doi: 10.1002/anie.202011367. PMID:33035363^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.