1emj
URACIL-DNA GLYCOSYLASE BOUND TO DNA CONTAINING A 4'-THIO-2'DEOXYURIDINE ANALOG PRODUCT
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OverviewOverview
Enzymatic transformations of macromolecular substrates such as DNA repair, enzyme/DNA transformations are commonly interpreted primarily by, active-site functional-group chemistry that ignores their extensive, interfaces. Yet human uracil-DNA glycosylase (UDG), an archetypical enzyme, that initiates DNA base-excision repair, efficiently excises the damaged, base uracil resulting from cytosine deamination even when active-site, functional groups are deleted by mutagenesis. The 1.8-A resolution, substrate analogue and 2.0-A resolution cleaved product cocrystal, structures of UDG bound to double-stranded DNA suggest enzyme-DNA, substrate-binding energy from the macromolecular interface is funneled, into catalytic power at the active site. The architecturally stabilized, closing of UDG enforces distortions of the uracil and deoxyribose in the, flipped-out nucleotide substrate that are relieved by glycosylic bond, cleavage in the product complex. This experimentally defined substrate, stereochemistry implies the enzyme alters the orientation of three, orthogonal electron orbitals to favor electron transpositions for, glycosylic bond cleavage. By revealing the coupling of this anomeric, effect to a delocalization of the glycosylic bond electrons into the, uracil aromatic system, this structurally implicated mechanism resolves, apparent paradoxes concerning the transpositions of electrons among, orthogonal orbitals and the retention of catalytic efficiency despite, mutational removal of active-site functional groups. These UDG/DNA, structures and their implied dissociative excision chemistry suggest, biology favors a chemistry for base-excision repair initiation that, optimizes pathway coordination by product binding to avoid the release of, cytotoxic and mutagenic intermediates. Similar excision chemistry may, apply to other biological reaction pathways requiring the coordination of, complex multistep chemical transformations.
DiseaseDisease
Known diseases associated with this structure: Immunodeficiency with hyper IgM, type 4 OMIM:[191525]
About this StructureAbout this Structure
1EMJ is a Single protein structure of sequence from Homo sapiens with URA as ligand. Active as Uridine nucleosidase, with EC number 3.2.2.3 Full crystallographic information is available from OCA.
ReferenceReference
Uracil-DNA glycosylase-DNA substrate and product structures: conformational strain promotes catalytic efficiency by coupled stereoelectronic effects., Parikh SS, Walcher G, Jones GD, Slupphaug G, Krokan HE, Blackburn GM, Tainer JA, Proc Natl Acad Sci U S A. 2000 May 9;97(10):5083-8. PMID:10805771
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