6ig1

DNA polymerase IV - DNA ternary complex 10

spinqualitylabelsall models 6ig1, resolution 1.97Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 6ig1 is a 6 chain structure with sequence from Escherichia coli K-12. This structure supersedes the now removed PDB entry 5yv4. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 1.97Å Ligands: DPO, MG, TTP Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function DPO4_ECOLI Poorly processive, error-prone DNA polymerase involved in untargeted mutagenesis. Copies undamaged DNA at stalled replication forks, which arise in vivo from mismatched or misaligned primer ends. These misaligned primers can be extended by PolIV. Exhibits no 3'-5' exonuclease (proofreading) activity. Overexpression of polIV results in increased frameshift mutagenesis. It is required for stationary-phase adaptive mutation, which provides the bacterium with flexibility in dealing with environmental stress, enhancing long-term survival and evolutionary fitness. May be involved in translesional synthesis, in conjunction with the beta clamp from PolIII. Publication Abstract from PubMed DNA synthesis by DNA polymerases (dPols) is central to duplication and maintenance of the genome in all living organisms. dPols catalyze the formation of a phosphodiester bond between the incoming deoxynucleoside triphosphate and the terminal primer nucleotide with the release of a pyrophosphate (PPi) group. It is believed that formation of the phosphodiester bond is an endergonic reaction and PPi has to be hydrolyzed by accompanying pyrophosphatase enzymes to ensure that the free energy change of the DNA synthesis reaction is negative and it can proceed in the forward direction. The fact that DNA synthesis proceeds in vitro in the absence of pyrophosphatases represents a long-standing conundrum regarding the thermodynamics of the DNA synthesis reaction. Using time-resolved crystallography, we show that hydrolysis of PPi is an intrinsic and critical step of the DNA synthesis reaction catalyzed by dPols. The hydrolysis of PPi occurs after the formation of the phosphodiester bond and ensures that the DNA synthesis reaction is energetically favorable without the need for additional enzymes. Also, we observe that DNA synthesis is a two Mg2+ ion assisted stepwise associative SN2 reaction. Overall, this study provides deep temporal insight regarding the primary enzymatic reaction responsible for genome duplication. Pyrophosphate hydrolysis is an intrinsic and critical step of the DNA synthesis reaction.,Kottur J, Nair DT Nucleic Acids Res. 2018 Jul 6;46(12):5875-5885. doi: 10.1093/nar/gky402. PMID:29850882 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also DNA polymerase 3D structures

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