The structural basis of RNA-catalyzed RNA polymerization
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 tr...
| Main Authors: | , , |
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| Other Authors: | |
| Format: | Article |
| Language: | en_US |
| Published: |
Elsevier B.V.
2014
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| Online Access: | http://hdl.handle.net/1721.1/83621 https://orcid.org/0000-0002-3872-2856 |
| Summary: | 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. |
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