1t4a
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(New page: 200px<br /><applet load="1t4a" size="450" color="white" frame="true" align="right" spinBox="true" caption="1t4a, resolution 2.00Å" /> '''Structure of B. Subt...)
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Revision as of 00:51, 21 November 2007
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Structure of B. Subtilis PurS C2 Crystal Form
Overview
Formylglycinamide ribonucleotide amidotransferase (FGAR-AT) catalyzes the, conversion of formylglycinamide ribonucleotide (FGAR), ATP, and glutamine, to formylglycinamidine ribonucleotide (FGAM), ADP, P(i), and glutamate in, the fourth step of the purine biosynthetic pathway. PurL exists in two, forms: large PurL (lgPurL) is a single chain, multidomain enzyme of about, 1300 amino acids, whereas small PurL (smPurL) contains about 800 amino, acids but requires two additional gene products, PurS and PurQ, for, activity. smPurL contains the ATP and FGAR binding sites, PurQ is a, glutaminase, and the function of PurS is just now becoming understood. We, determined the structure of Bacillus subtilis PurS in two different, crystal forms P2(1) and C2 at 2.5 and 2.0 A resolution, respectively. PurS, forms a tight dimer with a central six-stranded beta-sheet flanked by four, helices. In both the P2(1) and the C2 crystal forms, the quaternary, structure of PurS is a tetramer. The concave faces of the PurS dimers, interact via the C-terminal region to form a twelve-stranded beta-barrel, with a hydrophilic core. We used the structure of PurS together with the, structure of lgPurL from Salmonella typhimurium to construct a model of, the PurS/smPurL/PurQ complex. The HisH (glutaminase) domain of imidazole, glycerol phosphate synthetase was used as an additional model of PurQ. The, model shows stoichiometry of 2PurS/smPurL/PurQ using a PurS dimer or, 4PurS/2smPurL/2PurQ using a PurS tetramer. Both models place key conserved, residues at the ATP/FGAR binding site and at a structural ADP binding, site. The homology model is consistent with biochemical studies on the, reconstituted complex.
About this Structure
1T4A is a Single protein structure of sequence from Bacillus subtilis. Full crystallographic information is available from OCA.
Reference
A model for the Bacillus subtilis formylglycinamide ribonucleotide amidotransferase multiprotein complex., Anand R, Hoskins AA, Bennett EM, Sintchak MD, Stubbe J, Ealick SE, Biochemistry. 2004 Aug 17;43(32):10343-52. PMID:15301532
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