4eug | pdb_00004eug

Crystallographic and Enzymatic Studies of an Active Site Variant H187Q of Escherichia Coli Uracil DNA Glycosylase: Crystal Structures of Mutant H187Q and its Uracil Complex

spinqualitylabelsall models 4eug, resolution 1.40Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4eug is a 1 chain structure with sequence from Escherichia coli (strain b). Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Related: 2eug, 3eug, 5eug Gene: UNG (Escherichia coli (strain B)) Activity: Uridine nucleosidase, with EC number 3.2.2.3 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [UNG_ECOLI] Excises uracil residues from the DNA which can arise as a result of misincorporation of dUMP residues by DNA polymerase or due to deamination of cytosine.[HAMAP-Rule:MF_00148] 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 The nature of the putative general acid His187 in the reaction catalyzed by Escherichia coli uracil DNA glycosylase (UDG) was investigated using X-ray crystallography and NMR spectroscopy. The crystal structures of H187Q UDG, and its complex with uracil, have been solved at 1.40 and 1.60 A resolution, respectively. The structures are essentially identical to those of the wild-type enzyme, except that the side chain of Gln187 is turned away from the uracil base and cannot interact with uracil O2. This result provides a structural basis for the similar kinetic properties of the H187Q and H187A enzymes. The ionization state of His187 was directly addressed with (1)H-(15)N NMR experiments optimized for histidine ring spin systems, which established that His187 is neutral in the catalytically active state of the enzyme (pK(a) <5.5). These NMR experiments also show that His187 is held in the N(epsilon)()2-H tautomeric form, consistent with the crystallographic observation of a 2.9 A hydrogen bond from the backbone nitrogen of Ser189 to the ring N(delta)()1 of His187. The energetic cost of breaking this hydrogen bond may contribute significantly to the low pK(a) of His187. Thus, the traditional view that a cationic His187 donates a proton to uracil O2 is incorrect. Rather, we propose a concerted mechanism involving general base catalysis by Asp64 and electrophilic stabilization of the developing enolate on uracil O2 by a neutral His187. Heteronuclear NMR and crystallographic studies of wild-type and H187Q Escherichia coli uracil DNA glycosylase: electrophilic catalysis of uracil expulsion by a neutral histidine 187.,Drohat AC, Xiao G, Tordova M, Jagadeesh J, Pankiewicz KW, Watanabe KA, Gilliland GL, Stivers JT Biochemistry. 1999 Sep 14;38(37):11876-86. PMID:10508390 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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