CRYSTAL STRUCTURES OF POLYKETIDE MEGA-SYNTHASE

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 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. 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. 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.