Related Experiment Video
Updated: Feb 7, 2026

Probing High-density Functional Protein Microarrays to Detect Protein-protein Interactions
Published on: August 2, 2015
Probing the coordination and function of Fe4S4 modules in nitrogenase assembly protein NifB
Lee A Rettberg1, Jarett Wilcoxen2, Chi Chung Lee1
1Department of Molecular Biology and Biochemistry, University of California, Irvine, CA, 92697-3900, USA.
Abstract:
NifB is an essential radical S-adenosylmethionine (SAM) enzyme for nitrogenase cofactor assembly. Previous studies show that NifB couples a putative pair of [Fe4S4] modules (designated K1 and K2) into an [Fe8S9C] cofactor precursor concomitant with radical SAM-dependent carbide insertion through the action of its SAM-binding [Fe4S4] module. However, the coordination and function of the NifB cluster modules remain unknown. Here, we use continuous wave and pulse electron paramagnetic resonance spectroscopy to show that K1- and K2-modules are 3-cysteine-coordinated [Fe4S4] clusters, with a histidine-derived nitrogen serving as the fourth ligand to K1 that is lost upon K1/K2-coupling. Further, we demonstrate that coexistence of SAM/K2-modules is a prerequisite for methyltransfer to K2 and hydrogen abstraction from the K2-associated methyl by a 5'-deoxyadenosyl radical. These results establish an important framework for mechanistic explorations of NifB while highlighting the utility of a synthetic-cluster-based reconstitution approach employed herein in functional analyses of iron-sulfur (FeS) enzymes.
More Related Videos
09:59Functional Reconstitution and Channel Activity Measurements of Purified Wildtype and Mutant CFTR Protein
Published on: March 9, 2015
14:49A Quantitative Dot Blot Assay for AAV Titration and Its Use for Functional Assessment of the Adeno-associated Virus Assembly-activating Proteins
Published on: June 12, 2018
Related Concept Videos
Protein Complex Assembly
Many viruses self-assemble into a fully functional unit using the infected host cell to...
Protein Complex Assembly
Structural Protein Function
Collagen, the most abundant protein in mammals, is found throughout the body. In connective tissue, such as skin, ligaments, and tendons, it provides tensile strength and elasticity. In bones and teeth, it mineralizes to...
Coordination Number and Geometry
Mechanical Protein Functions
Coordination Compounds and Nomenclature