1p3w
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(New page: 200px<br /><applet load="1p3w" size="450" color="white" frame="true" align="right" spinBox="true" caption="1p3w, resolution 2.1Å" /> '''X-ray crystal structu...)
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Revision as of 21:20, 20 November 2007
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X-ray crystal structure of E. coli IscS
Overview
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.
About this Structure
1P3W is a Single protein structure of sequence from Escherichia coli with PLP as ligand. Full crystallographic information is available from OCA.
Reference
Crystal structure of IscS, a cysteine desulfurase from Escherichia coli., Cupp-Vickery JR, Urbina H, Vickery LE, J Mol Biol. 2003 Jul 25;330(5):1049-59. PMID:12860127
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