7C8M

Crystal structure of IscU wild-type

Summary for 7C8M

• Entry DOI: 10.2210/pdb7c8m/pdb
• Descriptor: Nitrogen-fixing NifU domain protein, FE2/S2 (INORGANIC) CLUSTER (2 entities in total)
• Functional Keywords: iron-sulfur cluster biogenesis, biosynthetic protein
• Biological source: Methanothrix thermoacetophila
• Total number of polymer chains: 2
• Total formula weight: 30880.56

Authors

Kunichika, K.,Takahashi, Y.,Fujishiro, T. (deposition date: 2020-06-03, release date: 2021-05-26, Last modification date: 2023-11-29)

Primary citation

Kunichika, K.,Nakamura, R.,Fujishiro, T.,Takahashi, Y.
The Structure of the Dimeric State of IscU Harboring Two Adjacent [2Fe-2S] Clusters Provides Mechanistic Insights into Cluster Conversion to [4Fe-4S].
Biochemistry, 60:1569-1572, 2021

PubMed Abstract: IscU serves as a scaffold for the assembly of a [2Fe-2S] cluster prior to its delivery to recipient protein. It has also been proposed that on one dimer of bacterial IscU, two [2Fe-2S] clusters can be converted into a single [4Fe-4S] cluster. However, lack of structural information about the dimeric state of IscU has hindered our understanding of the underlying mechanisms. In this study, we determine the X-ray crystal structure of IscU from the thermophilic archaeon and demonstrate a dimer structure of IscU in which two [2Fe-2S] clusters are facing each other in close proximity at the dimer interface. Our structure also reveals for the first time that Asp40 serves as a fourth ligand to the [2Fe-2S] cluster with three Cys ligands in each monomer, consistent with previous spectroscopic data. We confirm by EPR spectroscopic analysis that in solution two adjacent [2Fe-2S] clusters in the wild-type dimer are converted to a [4Fe-4S] cluster via reductive coupling. Furthermore, we find that the H106A substitution abolishes the reductive conversion to the [4Fe-4S] cluster without structural alteration, suggesting that His106 is functionally involved in this process. Overall, these findings provide a structural explanation for the assembly and conversion of Fe-S clusters on IscU and highlight a dynamic process that advances via association and dissociation of the IscU dimer.

PubMed: 33938220
DOI: 10.1021/acs.biochem.1c00112

Experimental method

X-RAY DIFFRACTION (3.5 Å)