STRUCTURAL ANALYSIS OF CARBON-CARBON BOND FORMATION CATALYZED BY RIBOZYME

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。大多数解决RNA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。我们已经确定了一种核酶的晶体结构，该核酶在未结合状态下和与反应产物的复合物中催化Diels-Alder反应形成对映选择性的碳-碳键。RNA采用了一种的嵌套假结结构，其预形成的催化口袋显示出与反应产物精确的形状互补性。RNA折叠和产物结合由广泛的堆叠和氢键决定，而立体选择由预制口袋的形状决定。催化作用显然是通过邻近性、互补性和电子效应的结合来实现的。我们观察到在独立进化的催化口袋架构的核酶和抗体催化的狄尔斯-阿尔德碳-碳键形成反应的结构平行。

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.