STRUCTURES OF RIBONUCLEOTIDE REDUCTASE

这个子项目是许多利用资源的研究子项目之一 由NIH/NCRR资助的中心拨款提供。子项目的主要支持 而子项目的主要调查员可能是由其他来源提供的， 包括其它NIH来源。 列出的子项目总成本可能 代表子项目使用的中心基础设施的估计数量， 而不是由NCRR赠款提供给子项目或子项目工作人员的直接资金。 核糖核苷酸还原酶（RR）通过将NDP还原为dNDP来催化从头DNA合成的限速步骤。 RR由一个容纳催化位点和两个变构位点的大的催化亚基和一个容纳自由基的亚基组成，自由基必须被递送到催化位点以启动催化。最近的数据显示，活性真核生物RR 1是六聚体，因此偏离了先前持有的活性RR 1二聚体的观点。ATP通过诱导RR 1六聚体激活RR，而dATP也通过诱导RR 1六聚体使RR失活。一个关键的问题，仍然有待回答的是，如何可以ATP是一个激活剂，而dATP的抑制剂，如果这两个效应诱导RR 1的六聚化？由于RR在dNTP合成中发挥的关键作用，它被靶向用于抗癌和病毒治疗。在过去，我们能够确定来自酵母的第一个真核RR 1结构（Xu et al.，2006 A和2006 B PNAS）和最近的人RRl（Fairman NSMB，2010）。在本提案中，我们将解决hRR 1-药物复合物的几种结构。我们还解决了第一个dATP结合的RR 1六聚体从酵母，虽然在6分之一的分辨率。我们希望扩展分辨率，以理解为什么dATP需要形成RR 1六聚体以形成RRRR。相比之下，ATP也形成RR 1六聚体，并作为RR的激活剂。我们希望确定RR 1-ATP六聚体的结构，以了解RR激活的机制。我们已经证明，小亚基RR 2的C-末端可以阻止RR组装。我们将解决RR 1与肽模拟物文库复合的结构，该肽模拟物文库阻断RR 1-RR 2缔合。

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.