STRUCTURES OF RIBONUCLEOTIDE REDUCTASE

这个子项目是利用资源的许多研究子项目之一。 由NIH/NCRR资助的中心拨款提供。对子项目的主要支持 子项目的首席调查员可能是由其他来源提供的， 包括美国国立卫生研究院的其他来源。为子项目列出的总成本可能 表示该子项目使用的中心基础设施的估计数量， 不是由NCRR赠款提供给次级项目或次级项目工作人员的直接资金。 核糖核苷酸还原酶(RR)催化从头合成DNA的限速步骤，将NDPs还原为dNDPs。RR由一个大的催化亚基和一个含有催化中心和两个变构中心的亚基，以及一个含有自由基的亚基组成，自由基必须输送到催化中心才能启动催化。最近的数据表明，活性的真核生物RR1是六聚体，因此与以前对活性RR1二聚体的看法不同。ATP通过诱导RR1六聚体激活RR，而dATP通过诱导RR1六聚体使RR失活。一个仍然有待回答的关键问题是，如果两个效应物都诱导RR1的六角化，那么ATP如何成为激活剂，而dATP如何成为抑制剂？由于RR在dNTP合成中起着关键作用，它被作为抗癌和病毒治疗的靶点。在过去，我们能够从酵母(Xu等人，2006A和2006B PNAS)和最近的人RR1(Fairman NSMB，2010)中确定第一个真核RR1结构。在这项提议中，我们将解决hRR1-药物络合物的几种结构。我们还从酵母中解决了第一个dATP结合的RR1六聚体，尽管分辨率为6？我们希望延长分辨率，以便了解为什么dATP需要形成RR1六聚体来灭活RR。相反，ATP也形成RR1六聚体，并作为RR的激活剂。我们希望通过测定RR1-ATP六聚体结构来了解RR激活的机制。我们已经证明，称为RR2的小亚基的C末端可以阻止RR组装。我们将解决RR1的结构与阻止RR1-RR2结合的模拟多肽文库。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Ribonucleotide reductase (RR) catalyzes the rate-limiting step of de novo DNA synthesis by reducing NDPs to dNDPs. RR composes of a large catalytic ¿ subunit that houses the catalytic site and two allosteric sites, and a ¿ subunit that houses a free-radical that must be delivered to the catalytic site to initiate catalysis. Recent data show that the active eukaryotic RR1 is hexameric, hence departing from a previously held view of active RR1 dimers. ATP activates RR by inducing RR1 hexamers, while dATP inactivates RR by also inducing RR1 hexamers. One of the key questions that still remain to be answered is how can ATP be an activator while dATP an inhibitor if both effectors induce hexamerization of RR1? Due to the crucial role played by RR in dNTP synthesis, it is targeted for anti-cancer and viral therapy. In the past, we were able to determine the first eukaryotic RR1 structure from yeast (Xu et al., 2006A and 2006B PNAS) and recently the human RR1 (Fairman NSMB, 2010). During this proposal we will solve several structures of hRR1-drug complexes. We have also solved the first dATP-bound RR1 hexamer from yeast, albeit at 6 ¿ resolution. We wish to extend the resolution in order to understand why it is required for dATP to form RR1 hexamers to inactivate RR. In contrast ATP also forms RR1 hexamers and act as an activator of RR. We wish to determine the RR1-ATP hexamer structure to understand the mechanism of RR activation. We have shown that the C-terminus of the small subunit called RR2 can block RR assembly. We will solve structures of RR1 complexed with peptidomimetic libraries that block RR1-RR2 association.