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Mycobacterial DNA polymerase I: activities and crystal structures of the POL domain as apoenzyme and in complex with a DNA primer-template and of the full-length FEN/EXO–POL enzyme

机译:分枝杆菌DNA聚合酶I:POL结构域的活性和晶体结构作为脱辅酶并与DNA引物模板和全长FEN / EXO-POL酶复合

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摘要

Mycobacterial Pol1 is a bifunctional enzyme composed of an N-terminal DNA flap endonuclease/5′ exonuclease domain (FEN/EXO) and a C-terminal DNA polymerase domain (POL). Here we document additional functions of Pol1: FEN activity on the flap RNA strand of an RNA:DNA hybrid and reverse transcriptase activity on a DNA-primed RNA template. We report crystal structures of the POL domain, as apoenzyme and as ternary complex with 3′-dideoxy-terminated DNA primer-template and dNTP. The thumb, palm, and fingers subdomains of POL form an extensive interface with the primer-template and the triphosphate of the incoming dNTP. Progression from an open conformation of the apoenzyme to a nearly closed conformation of the ternary complex entails a disordered-to-ordered transition of several segments of the thumb and fingers modules and an inward motion of the fingers subdomain—especially the O helix—to engage the primer-template and dNTP triphosphate. Distinctive structural features of mycobacterial Pol1 POL include a manganese binding site in the vestigial 3′ exonuclease subdomain and a non-catalytic water-bridged magnesium complex at the protein-DNA interface. We report a crystal structure of the bifunctional FEN/EXO–POL apoenzyme that reveals the positions of two active site metals in the FEN/EXO domain.
机译:分枝杆菌Pol1是一种双功能酶,由N端DNA瓣内切核酸酶/ 5'核酸外切酶结构域(FEN / EXO)和C端DNA聚合酶结构域(POL)组成。在这里,我们记录了Pol1的其他功能:RNA:DNA杂化物的瓣状RNA链上的FEN活性和DNA引发的RNA模板上的逆转录酶活性。我们报告POL结构域的晶体结构,作为脱辅酶和与3'-双脱氧终止的DNA引物模板和dNTP的三元复合物。 POL的拇指,手掌和手指子域与引物模板和传入的dNTP的三磷酸酯形成广泛的界面。从脱辅基辅酶的开放构象到三元复合物的近乎封闭的构象的发展,使拇指和手指模块的几个节段从无序到有序过渡以及手指子域(尤其是O螺旋)的向内运动来参与引物模板和dNTP三磷酸酯。分枝杆菌Pol1 POL的独特结构特征包括在残留的3'核酸外切酶亚结构域中的锰结合位点和在蛋白质-DNA界面处的非催化水桥镁复合物。我们报告了双功能FEN / EXO-POL脱辅酶的晶体结构,揭示了FEN / EXO域中两个活性位点金属的位置。

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