6y88

IGPS (Indole-3-glycerol phosphate synthase) from Pseudomonas aeruginosa in complex with substrate inhibitor rCdRP

spinqualitylabelsall models 6y88, resolution 2.10Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 6y88 is a 8 chain structure with sequence from Pseudomonas aeruginosa. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.0998344Å Ligands: 137, CIT, GOL, PO4 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function TRPC_PSEAE Publication Abstract from PubMed In tryptophan biosynthesis, the reaction catalyzed by the enzyme indole-3-glycerol phosphate synthase (IGP synthase, IGPS) starts with a condensation step where the substrate's carboxylated phenyl group makes a nucleophilic attack to form the pyrrole ring of the indole, followed by a decarboxylation which restores the aromaticity of the phenyl. IGPS from Pseudomonas aeruginosa has the highest turnover number of all characterized IGPS enzymes, providing an excellent model system to test the necessity of the decarboxylation step. This step was since the 1960s considered to be mechanistically essential based on studies of the IGPS:PRAI fusion protein from Escherichia coli. Here, we present the crystal structure of P. aeruginosa IGPS in complex with reduced CdRP, a non-reactive substrate analogue, and using a sensitive discontinuous assay, we demonstrate weak promiscuous activity on the decarboxylated substrate 1-(phenylamino)-1-deoxyribulose-5-phosphate (PAdRP) - with approximately 1000' lower rate of IGP formation than from the native substrate. We also show that E. coli IGPS, at even lower rate, can produce IGP from decarboxylated substrate. Our structure of P. aeruginosa IGPS has eight molecules in the asymmetric unit, out of which seven contain ligand, and one displays a previously unobserved conformation closer to the reactive state. One of the few non-conserved active-site residues, Phe201 in P. aeruginosa IGPS, is by mutagenesis demonstrated to be important for the higher turnover of this enzyme on both substrates. Our results demonstrate that, despite IGPS's classification as a carboxylyase (i.e. decarboxylase), decarboxylation not a completely essential step in its catalysis. Structure and kinetics of indole-3-glycerol phosphate synthase from Pseudomonas aeruginosa - decarboxylation is not essential for indole formation.,Soderholm A, Newton MS, Patrick WM, Selmer M J Biol Chem. 2020 Sep 14. pii: RA120.014936. doi: 10.1074/jbc.RA120.014936. PMID:32928960 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also IGPS 3D structures

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