Abstract of the PDB Structure's related Publication:
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.
IscA is a scaffold protein for the [Fe-S] clusters. It binds ferredoxin, iron and [2Fe-2S] clusters, and participates in the biosynthesis of iron-sulfur proteins, including (dimethylallyl)adenosine tRNA methylthiotransferase MiaB. IscA homolog in human is IscA1, however its function is not clear.