CRYSTAL STRUCTURES OF POLYKETIDE MEGA-SYNTHASE

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。 聚酮类化合物包括许多重要的降胆固醇药物(如洛伐他汀)、抗癌药物(如阿霉素和博莱菌素)和抗生素活性药物(如四环素和红霉素)，具有潜在的HIV应用前景。聚酮合成酶(PKS)是一种多结构域的酶复合体，通过可控的构筑单元和修饰反应(包括链还原和环化)产生大量的聚酮。在PKS活性的结构和分子基础上有一个关键的缺口。为了解决PKS络合物的结构问题，我们结晶了几个衍射峰为1.7？2.8？的PKS络合物。由于这些络合物的大小，我们不能用单域结构的分子置换来解决它们。我们已经将PKS络合物晶化为Se、Au和Pt衍生物，其内部衍射率为2.2？4.0？因此，SSRL的Beamtime将产生巨大的影响，帮助我们将这个令人兴奋的项目带到终点线。作为拟议研究的结果，我们希望确定所有三个多结构域复杂结构，并确定蛋白质-蛋白质相互作用对聚酮环化/终止特异性的重要性。聚酮基环对聚酮类化合物的抗菌和抗癌性能至关重要。在这项申请中提出的研究具有重要意义，因为它的结果使我们能够阐明聚酮是如何在分子水平上被特定地环化和终止的，这是以前从未被可视化过的。从长远来看，这项提议的结果将通过PKS的结构定向突变体提供医学上有用的化学物质，从而对公众健康产生重大的积极影响。

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. Polyketides include many important drugs with cholesterol-lowering (such as lovastatin), anticancer (such as doxorubicin and bleomysin) and antibiotic activities (such as tetracycline and erythromycin) with potential HIV applications. Polyketide synthase (PKS) is a multi-domain enzyme complex that produces a huge variety of polyketides via a controlled variation of building blocks and modification reactions, including chain reduction and cyclization. There is a critical gap in the structure and molecular basis of PKS activity. To solve the PKS complex structures, we have crystallized several PKS complexes that diffract to 1.7 ? 2.8 ¿. Because of the size of these complexes, we could not solve them by molecular replacement using single-domain structures. We have already crystallized the PKS complexes as Se, Au and Pt derivatives that diffract in-house to 2.2 ? 4.0 ¿. Therefore, beamtime at SSRL will have a great impact by helping us bring this exciting project to the finish line. As an outcome of the proposed investigations, we expect to determine all three multi-domain complex structures and determine the importance of protein-protein interaction on the polyketide cyclization/termination specificity. The polyketide ring is vital for the antibiotic and anticancer properties of polyketides. The research proposed in this application is significant, because its outcome allows us to elucidate how polyketides are specifically cyclized and terminated at a molecular level that has not been visualized before. In the long run, the result from this proposal will have a significant positive impact on the public health by providing medically useful chemicals via structure-directed mutants of PKS.