Motif D of Viral RNA-Dependent RNA Polymerases Determines Efficiency and Fidelity of Nucleotide Addition

作者：Yang Xiaorong; Smidansky Eric D; Maksimchuk Kenneth R; Lum David; Welch Jesse L; Arnold Jamie J; Cameron Craig E; Boehr David D^*

来源：Structure, 2012, 20(9): 1519-1527.

DOI：10.1016/j.str.2012.06.012

Fast, accurate nucleotide incorporation by polymerases facilitates expression and maintenance of genomes. Many polymerases use conformational dynamics of a conserved a helix to permit efficient nucleotide addition only when the correct nucleotide substrate is bound. This a helix is missing in structures of RNA-dependent RNA polymerases (RdRps) and RTs. Here, we use solution-state nuclear magnetic resonance to demonstrate that the conformation of conserved structural motif D of an RdRp is linked to the nature (correct versus incorrect) of the bound nucleotide and the protonation state of a conserved, motif-D lysine. Structural data also reveal the inability of motif D to achieve its optimal conformation after incorporation of an incorrect nucleotide. Functional data are consistent with the conformational change of motif D becoming rate limiting during and after nucleotide misincorporation. We conclude that motif D of RdRps and, by inference, RTs is the functional equivalent to the fidelity helix of other polymerases.

• 出版日期2012-9-5