Batra Vinod K, Beard William A, Pedersen Lars C, Wilson Samuel H
Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709-12233, USA.
Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709-12233, USA.
Structure. 2016 Nov 1;24(11):1863-1875. doi: 10.1016/j.str.2016.08.006. Epub 2016 Sep 15.
High-fidelity DNA synthesis requires that polymerases display a strong preference for right nucleotide insertion. When the wrong nucleotide is inserted, the polymerase deters extension from the mismatched DNA terminus. Twenty-three crystallographic structures of DNA polymerase β with terminal template-primer mismatches were determined as binary DNA and ternary pre-catalytic substrate complexes. These structures indicate that the mismatched termini adopt various distorted conformations that attempt to satisfy stacking and hydrogen-bonding interactions. The binary complex structures indicate an induced strain in the mismatched template nucleotide. Addition of a non-hydrolyzable incoming nucleotide stabilizes the templating nucleotide with concomitant strain in the primer terminus. Several dead-end ternary complex structures suggest that DNA synthesis might occur as the enzyme transitions from an open to a closed complex. The structures are consistent with an induced-fit mechanism where a mismatched terminus is misaligned relative to the correct incoming nucleotide to deter or delay further DNA synthesis.
高保真DNA合成要求聚合酶对正确核苷酸的插入表现出强烈偏好。当错误的核苷酸被插入时，聚合酶会阻止从不匹配的DNA末端进行延伸。测定了23种具有末端模板-引物错配的DNA聚合酶β的晶体结构，分别作为二元DNA和三元预催化底物复合物。这些结构表明，错配末端采用了各种扭曲构象，试图满足堆积和氢键相互作用。二元复合物结构表明错配模板核苷酸中存在诱导应变。添加不可水解的进入核苷酸会稳定模板核苷酸，同时引物末端出现应变。几个终产物三元复合物结构表明，DNA合成可能在酶从开放复合物转变为封闭复合物时发生。这些结构与诱导契合机制一致，即错配末端相对于正确的进入核苷酸未对齐，以阻止或延迟进一步的DNA合成。
