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Updated: Aug 29, 2026

Combining X-Ray Crystallography with Small Angle X-Ray Scattering to Model Unstructured Regions of Nsa1 from S. Cerevisiae
Published on: January 10, 2018
Crystal structure of the ancient, Fe-S scaffold IscA reveals a novel protein fold
Patrick W Bilder1, Huangen Ding, Marcia E Newcomer
1Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
Abstract:
IscA belongs to an ancient family of proteins responsible for iron-sulfur cluster assembly in essential metabolic pathways preserved throughout evolution. We report here the 2.3 A resolution crystal structure of Escherichia coli IscA, a novel fold in which mixed beta-sheets form a compact alpha-beta sandwich domain. In contrast to the highly mobile secondary structural elements within the bacterial Fe-S scaffold protein IscU, a protein which is thought to have a similar function, the great majority of the amino acids that are conserved in IscA homologues are located in elements that constitute a well-ordered fold. However, the 10-residue C-terminal tail segment that contains two invariant cysteines critical for the Fe-S-binding function of a cyanobacterial (Synechocystis PCC) IscA homologue is not ordered in our structure. In addition, the crystal packing reveals a helical assembly that is constructed from two possible tetrameric oligomers of IscA.
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