1X0G

Crystal Structure of IscA with the [2Fe-2S] cluster

Summary for 1X0G

• Entry DOI: 10.2210/pdb1x0g/pdb
• Descriptor: IscA, SODIUM ION, FE2/S2 (INORGANIC) CLUSTER, ... (4 entities in total)
• Functional Keywords: [2fe-2s], biosynthesis, cyanobacteria, domain swapping, fe-s cluster, iron, iron-sulfur cluster protein, isc, isca, scaffold, sulfur, tetrameric, three conserved cys, metal binding protein
• Biological source: Thermosynechococcus elongatus
• Total number of polymer chains: 4
• Total formula weight: 49869.94

Authors

Morimoto, K.,Yamashita, E.,Kondou, Y.,Lee, S.J.,Tsukihara, T.,Nakai, M. (deposition date: 2005-03-22, release date: 2006-06-06, Last modification date: 2024-03-13)

Primary citation

Morimoto, K.,Yamashita, E.,Kondou, Y.,Lee, S.J.,Arisaka, F.,Tsukihara, T.,Nakai, M.
The Asymmetric IscA Homodimer with an Exposed [2Fe-2S] Cluster Suggests the Structural Basis of the Fe-S Cluster Biosynthetic Scaffold.
J.Mol.Biol., 360:117-132, 2006

PubMed Abstract: It has been shown that the so-called scaffold proteins are vital in Fe-S cluster biosynthesis by providing an intermediate site for the assembly of Fe-S clusters. However, since no structural information on such scaffold proteins with bound Fe-S cluster intermediates is available, the structural basis of the core of Fe-S cluster biosynthesis remains poorly understood. Here we report the first Fe-S cluster-bound crystal structure of a scaffold protein, IscA, from Thermosynechococcus elongatus, which carries three strictly conserved cysteine residues. Surprisingly, one partially exposed [2Fe-2S] cluster is coordinated by two conformationally distinct IscA protomers, termed alpha and beta, with asymmetric cysteinyl ligation by Cys37, Cys101, Cys103 from alpha and Cys103 from beta. In the crystal, two alphabeta dimers form an unusual domain-swapped tetramer via central domains of beta protomers. Together with additional biochemical data supporting its physiologically relevant configuration, we propose that the unique asymmetric Fe-S cluster coordination and the resulting distinct conformational stabilities of the two IscA protomers are central to the function of IscA-type Fe-S cluster biosynthetic scaffold.

PubMed: 16730357
DOI: 10.1016/j.jmb.2006.04.067

Experimental method

X-RAY DIFFRACTION (2.5 Å)