1X0G: Crystal Structure Of Isca With The [2fe-2s] Cluster

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.
PDB ID: 1X0GDownload
MMDB ID: 38924
PDB Deposition Date: 2005/3/22
Updated in MMDB: 2012/10
Experimental Method:
x-ray diffraction
Resolution: 2.5  Å
Source Organism:
Similar Structures:
Biological Unit for 1X0G: tetrameric; determined by author and by software (PISA)
Molecular Components in 1X0G
Label Count Molecule
Proteins (4 molecules)
Molecule annotation
Chemicals (4 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB