4dqi | pdb_00004dqi

Ternary complex of Bacillus DNA Polymerase I Large Fragment, DNA duplex, and dCTP (paired with dG of template)

spinqualitylabelsall models 4dqi, resolution 1.69Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4dqi is a 6 chain structure with sequence from Geobacillus kaustophilus HTA426 and Synthetic construct. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: DCP, DOC, MG, SO4 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [Q5KWC1_GEOKA] Publication Abstract from PubMed In addition to discriminating against base-pair mismatches, DNA polymerases exhibit a high degree of selectivity for deoxyribonucleotides over ribo- or dideoxy nucleotides. It has been proposed that a single active site residue (steric gate) blocks productive binding of nucleotides containing 2' hydroxyls. Although this steric gate plays a role in sugar moiety discrimination, its interactions do not account fully for the observed behavior of mutants. Here we present ten high-resolution crystal structures and enzyme kinetic analyses of Bacillus DNA polymerase I large fragment (BF) variants complexed with deoxy-, ribo-, dideoxy-nucleotides, and a DNA substrate. Taken together, these data present a more nuanced and general mechanism for nucleotide discrimination in which ensembles of intermediate conformations in the active site trap non-cognate substrates. It is known that the active site O-helix transitions from an open state in the absence of nucleotide substrates to a ternary complex closed state in which the reactive groups are aligned for catalysis. Substrate misalignment in the closed state plays a fundamental part in preventing non-cognate nucleotide misincorpation. The structures presented here show that additional O-helix conformations intermediate between the open and closed state extremes create an ensemble of binding sites that trap and misalign non-cognate nucleotides. Water-mediated interactions, absent in the fully closed state, play an important role in formation of these binding sites, and can be remodeled to accommodate different non-cognate substrates. This mechanism may extend also to base-pair discrimination. Structural factors that determine selectivity of a high-fidelity DNA polymerase for deoxy-, dideoxy-, and ribo-nucleotides.,Wang W, Wu EY, Hellinga HW, Beese LS J Biol Chem. 2012 May 30. PMID:22648417 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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