The structural basis of RNA-catalyzed RNA polymerization
Author(s)Shechner, David M; Bartel, David; Shechner, David M.
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Early life presumably required polymerase ribozymes capable of replicating RNA. Known polymerase ribozymes best approximating such replicases use as their catalytic engine an RNA-ligase ribozyme originally selected from random RNA sequences. Here we report 3.15-Å crystal structures of this ligase trapped in catalytically viable preligation states, with the 3′-hydroxyl nucleophile positioned for in-line attack on the 5′-triphosphate. Guided by metal- and solvent-mediated interactions, the 5′-triphosphate hooks into the major groove of the adjoining RNA duplex in an unanticipated conformation. Two phosphates and the nucleophile jointly coordinate an active-site metal ion. Atomic mutagenesis experiments demonstrate that active-site nucleobase and hydroxyl groups also participate directly in catalysis, collectively playing a role that in proteinaceous polymerases is performed by a second metal ion. Thus artificial ribozymes can use complex catalytic strategies that differ markedly from those of analogous biological enzymes.
DepartmentMassachusetts Institute of Technology. Department of Biology; Whitehead Institute for Biomedical Research
Nature Structural & Molecular Biology
Shechner, David M, and David P Bartel. “The structural basis of RNA-catalyzed RNA polymerization.” Nature Structural & Molecular Biology 18, no. 9 (August 21, 2011): 1036-1042.
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