CRYSTAL STRUCTURE OF POLYKETIDE SYNTHASES: STRUCTURE-BASED DRUG DESIGN ON NOVEL

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。聚酮类化合物是一类结构多样的天然产物，具有重要的药理活性，如抗癌、抗生素、抗病毒和免疫抑制特性。（世界上最畅销的药物中有20%是聚酮类药物。）聚酮的生物合成是由聚酮合成酶（PKS）催化的，PKS通过酰基辅酶a硫酯之间的反复缩合来组装聚酮的碳骨架，因此聚酮结构的多样性部分源于不同的起始剂或扩展剂单元的加入，PKS中的酰基转移酶（AT）进行了起始剂和扩展剂单元的选择。对AT晶体结构的确定将极大地促进蛋白质工程或底物工程制备新型聚酮类化合物。迄今为止，仅在放线鸟肽聚酮合成酶中发现了丙二醇特异性AT (MAT)，而模块化pks中具有不同底物特异性的AT结构域的结构尚未得到解决，对其底物特异性的结构基础知之甚少。SSRL的光束时间将用于求解模块化PKS中MAT突变体、基质-MAT共晶和at结构域的晶体结构，旨在基于结构的新型聚酮设计。我们在SSRL利用光束时间的第二个主要发现是R1128聚酮合酶中功能未知的酶ZhuC的晶体结构。ZhuC序列与MAT同源；它被认为是R1128聚酮合酶中的酰基转移酶，但其实际功能尚不清楚。第三，我们目前正在进行完整的多道尔顿DEBS蛋白的结构测定。第四，我们将确定HLA-DQ2与导致乳糜泻的免疫原性α - 2肽复合物的晶体结构。

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 are a structurally diverse class of natural products that have pharmacologically important activities, such as anti-cancer, antibiotic, anti-virus, and immunosuppressive properties. (20% of the top selling drugs in the world are polyketides.) The biosynthesis of polyketides is catalyzed by polykeitde synthases(PKSs), which assemble the carbon backbones of polyketides through repeated condensations between acyl-CoA thioesters, so the diversity in polyketide structures is in part derived from the incorporation of different starter or extender units, selection of the starter and extender units is carried out by acyltransferase(AT) in PKS. Determination of the crystal structures of AT will greatly facilitate the production of novel polyketides by protein engineering or substrate-engineering. Thus far, only the malonyl-specific AT (MAT) in actinorhodin polyketide synthase has been crystallized, while none of the structures of AT domains with different substrate specificities in modular PKSs have been solved and little is known about the structural basis for their substrate specificities. Beam time at SSRL will be utilized to solve crystal structures of MAT mutants, substrate-MAT cocrystals and AT domains in modular PKS, aiming at structural-based novel polyketide design. Our second major discovery utilizing beam time at SSRL is the crystal structure of a functionally unknown enzyme ZhuC in R1128 polyketide synthase. The sequence of ZhuC is homologous to MAT; it was proposed to be the acyltransferase in R1128 polyketide synthase, but its actual function is still not clear. Third, we are currently persuing structure determination of an intact multidalton DEBS protein. Fourth, we will determine the crystal structure of HLA-DQ2 complexed with the immunogenic alpha2-peptide, that is responsible for celiac disease.