STRUCTURAL ANALYSIS OF CARBON-CARBON BOND FORMATION CATALYZED BY RIBOZYME

这个子项目是利用由NIH/NCRR资助的中心拨款提供的资源的许多研究子项目之一。子项目和调查员(PI)可能从另一个NIH来源获得了主要资金，因此可能会出现在其他CRISE条目中。列出的机构是针对中心的，而不一定是针对调查员的机构。大多数针对S催化功能的结构努力都集中在催化磷酸二酯转移反应的天然核酶上。相比之下，人们对RNA如何催化其他类型的化学反应知之甚少。我们测定了一种核酶的晶体结构，该核酶在非结合状态和与反应产物形成络合物的情况下，通过Diels-Alder反应催化不对称碳-碳键的形成。RNA采用？形嵌套伪结结构，其预先形成的催化口袋对反应产物显示精确的形状互补。RNA折叠和产物结合由广泛的堆积和氢键决定，而立体选择则由预成型口袋的形状决定。催化显然是通过接近、互补和电子效应的组合来实现的。我们观察到核酶和抗体催化的Diels-Alder碳-碳键形成反应的独立进化的催化口袋结构中的结构相似之处。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The majority of structural efforts addressing RNA¿¿¿s catalytic function have focused on natural ribozymes, which catalyze phosphodiester transfer reactions. By contrast, very little is known on how RNA can catalyze other types of chemical reactions. We have determined the crystal structures of a ribozyme that catalyzes enantioselective carbon-carbon bond formation by the Diels-Alder reaction in the unbound state and in complex with reaction product. The RNA adopts a ¿¿-shaped nested pseudoknot architecture, whose pre-formed catalytic pocket shows precise shape-complementarity to the reaction product. RNA folding and product binding are dictated by extensive stacking and hydrogen-bonding, while stereoselection is governed by the shape of the preformed pocket. Catalysis is apparently achieved by a combination of proximity, complementarity, and electronic effects. We observe structural parallels in the independently evolved catalytic pocket architectures for ribozyme- and antibody-catalyzed Diels-Alder carbon-carbon bond forming reactions.