3ctl | pdb_00003ctl

Crystal structure of D-Allulose 6-Phosphate 3-Epimerase from Escherichia coli K12 complexed with D-glucitol 6-phosphate and magnesium

spinqualitylabelsall models 3ctl, resolution 2.20Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3ctl is a 6 chain structure with sequence from "bacillus_coli"_migula_1895 "bacillus coli" migula 1895. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: MG, S6P Related: 3ct7 Gene: alsE, yjcU ("Bacillus coli" Migula 1895) Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [ALSE_ECOLI] Catalyzes the reversible epimerization of D-allulose 6-phosphate to D-fructose 6-phosphate. Can also catalyze with lower efficiency the reversible epimerization of D-ribulose 5-phosphate to D-xylulose 5-phosphate. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed Enzymes that share the (beta/alpha) 8-barrel fold catalyze a diverse range of reactions. Many utilize phosphorylated substrates and share a conserved C-terminal (beta/alpha) 2-quarter barrel subdomain that provides a binding motif for the dianionic phosphate group. We recently reported functional and structural studies of d-ribulose 5-phosphate 3-epimerase (RPE) from Streptococcus pyogenes that catalyzes the equilibration of the pentulose 5-phosphates d-ribulose 5-phosphate and d-xylulose 5-phosphate in the pentose phosphate pathway [J. Akana, A. A. Fedorov, E. Fedorov, W. R. P. Novack, P. C. Babbitt, S. C. Almo, and J. A. Gerlt (2006) Biochemistry 45, 2493-2503]. We now report functional and structural studies of d-allulose 6-phosphate 3-epimerase (ALSE) from Escherichia coli K-12 that catalyzes the equilibration of the hexulose 6-phosphates d-allulose 6-phosphate and d-fructose 6-phosphate in a catabolic pathway for d-allose. ALSE and RPE prefer their physiological substrates but are promiscuous for each other's substrate. The active sites (RPE complexed with d-xylitol 5-phosphate and ALSE complexed with d-glucitol 6-phosphate) are superimposable (as expected from their 39% sequence identity), with the exception of the phosphate binding motif. The loop following the eighth beta-strand in ALSE is one residue longer than the homologous loop in RPE, so the binding site for the hexulose 6-phosphate substrate/product in ALSE is elongated relative to that for the pentulose 5-phosphate substrate/product in RPE. We constructed three single-residue deletion mutants of the loop in ALSE, DeltaT196, DeltaS197 and DeltaG198, to investigate the structural bases for the differing substrate specificities; for each, the promiscuity is altered so that d-ribulose 5-phosphate is the preferred substrate. The changes in k cat/ K m are dominated by changes in k cat, suggesting that substrate discrimination results from differential transition state stabilization. In both ALSE and RPE, the phosphate group hydrogen bonds not only with the conserved motif but also with an active site loop following the sixth beta-strand, providing a potential structural mechanism for coupling substrate binding with catalysis. Structural basis for substrate specificity in phosphate binding (beta/alpha)8-barrels: D-allulose 6-phosphate 3-epimerase from Escherichia coli K-12.,Chan KK, Fedorov AA, Fedorov EV, Almo SC, Gerlt JA Biochemistry. 2008 Sep 9;47(36):9608-17. Epub 2008 Aug 14. PMID:18700786 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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