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1qr7
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(New page: 200px<br /><applet load="1qr7" size="450" color="white" frame="true" align="right" spinBox="true" caption="1qr7, resolution 2.6Å" /> '''CRYSTAL STRUCTURE OF ...)
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Revision as of 22:47, 20 November 2007
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CRYSTAL STRUCTURE OF PHENYLALANINE-REGULATED 3-DEOXY-D-ARABINO-HEPTULOSONATE-7-PHOSPHATE SYNTHASE FROM ESCHERICHIA COLI COMPLEXED WITH PB2+ AND PEP
Overview
BACKGROUND: In microorganisms and plants the first step in the common, pathway leading to the biosynthesis of aromatic compounds is the, stereospecific condensation of phosphoenolpyruvate (PEP) and, D-erythrose-4-phosphate (E4P) giving rise to, 3-deoxy-D-arabino-heptulosonate-7-phosphate (DAHP). This reaction is, catalyzed by DAHP synthase (DAHPS), a metal-activated enzyme, which in, microorganisms is the target for negative-feedback regulation by pathway, intermediates or by end products. In Escherichia coli there are three, DAHPS isoforms, each specifically inhibited by one of the three aromatic, amino acids. RESULTS: The crystal structure of the phenylalanine-regulated, form of DAHPS complexed with PEP and Pb2+ (DAHPS(Phe)-PEP-Pb) was, determined by multiple wavelength anomalous dispersion phasing utilizing, the anomalous scattering of Pb2+. The tetramer consists of two tight, dimers. The monomers of the tight dimer are coupled by extensive, interactions including a pair of three-stranded, intersubunit beta sheets., The monomer (350 residues) is a (beta/alpha)8 barrel with several, additional beta strands and alpha helices. The PEP and Pb2+ are at the, C-ends of the beta strands of the barrel, as is SO4(2-), inferred to, occupy the position of the phosphate of E4P. Mutations that reduce, feedback inhibition cluster about a cavity near the twofold axis of the, tight dimer and are centered approximately 15 A from the active site, indicating the location of a separate regulatory site. CONCLUSIONS: The, crystal structure of DAHPS(Phe)-PEP-Pb reveals the active site of this key, enzyme of aromatic biosynthesis and indicates the probable site of, inhibitor binding. This is the first reported structure of a DAHPS; the, structure of its two paralogs and of a variety of orthologs should now be, readily determined by molecular replacement.
About this Structure
1QR7 is a Single protein structure of sequence from Escherichia coli with PB, SO4 and PEP as ligands. Active as 3-deoxy-7-phosphoheptulonate synthase, with EC number 2.5.1.54 Full crystallographic information is available from OCA.
Reference
Crystal structure of phenylalanine-regulated 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase from Escherichia coli., Shumilin IA, Kretsinger RH, Bauerle RH, Structure. 1999 Jul 15;7(7):865-75. PMID:10425687
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