Crystal structure of IscS, a cysteine desulfurase from Escherichia coli.

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Cupp-Vickery JR, Urbina H, Vickery LE

Crystal structure of IscS, a cysteine desulfurase from Escherichia coli.

J Mol Biol. 2003 Jul 25;330(5):1049-59.

PubMed ID

12860127 [ View in PubMed

]

Abstract

IscS is a widely distributed cysteine desulfurase that catalyzes the pyridoxal phosphate-dependent desulfuration of L-cysteine and plays a central role in the delivery of sulfur to a variety of metabolic pathways. We report the crystal structure of Escherichia coli IscS to a resolution of 2.1A. The crystals belong to the space group P2(1)2(1)2(1) and have unit cell dimensions a=73.70A, b=101.97A, c=108.62A (alpha=beta=gamma=90 degrees ). Molecular replacement with the Thermotoga maritima NifS model was used to determine phasing, and the IscS model was refined to an R=20.6% (R(free)=23.6%) with two molecules per asymmetric unit. The structure of E.coli IscS is similar to that of T.maritima NifS with nearly identical secondary structure and an overall backbone r.m.s. difference of 1.4A. However, in contrast to NifS a peptide segment containing the catalytic cysteine residue (Cys328) is partially ordered in the IscS structure. This segment of IscS (residues 323-335) forms a surface loop directed away from the active site pocket. Cys328 is positioned greater than 17A from the pyridoxal phosphate cofactor, suggesting that a large conformational change must occur during catalysis in order for Cys328 to participate in nucleophilic attack of a pyridoxal phosphate-bound cysteine substrate. Modeling suggests that rotation of this loop may allow movement of Cys328 to within approximately 3A of the pyridoxal phosphate cofactor.

DrugBank Data that Cites this Article

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Pyridoxal phosphate	Cysteine desulfurase, mitochondrial	Protein	Humans	Unknown	Cofactor	Details