STRUCTURAL STUDIES OF ACYL CARRIER PROTEIN (SC0185)

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。 聚酮类化合物是结构多样、具有重要药用价值的天然产物。它们主要由细菌、真菌和植物作为次生代谢物产生，由世界上许多广泛使用的药物组成。链霉菌的多功能芳香族产物。如四环素和阿霉素是聚酮类化合物的一个重要亚类。芳香族聚酮是通过丙二酰辅酶A衍生的构建块之间的重复脱羧基缩合生物合成的。它们的合成是由II型聚酮合成酶(PKSS)催化的，PKS与细菌和植物中发现的II型脂肪酸合成酶具有共同的结构和机制。最小的II型PKS由四种蛋白质组成，包括酮合成酶(KS)、链长因子(CLF)、酰基载体蛋白(ACP)和丙二酰辅酶A：ACP转酰基酶(MAT)。KS和CLF形成杂二聚体，它催化连续的丙二酸基单元之间的缩合反应，并控制聚酮链的总长度。来自天蓝色链霉菌A3(2)的SCO1815是一种依赖于NADPH的酮还原酶的未知同源物，它识别和还原R1128 PKS起始模块中的β-酮酰基-ACP中间体。测定了SCO1815的X-射线晶体结构为2.0°。结构表明SCO1815采用Rossmann折叠，表明辅因子结合时发生了构象变化。我们认为由三个保守残基形成的带正电荷的斑块是ACP的对接位置。这些发现为将非天然的引物单元引入新型聚酮提供了新的工程机会。

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 structurally diverse and medicinally important natural products. They are produced as secondary metabolites primarily by bacteria, fungi, and plants and comprise many of the widely used drugs in the world. Polyfunctional aromatic products of Streptomyces spp. such as the tetracyclines and doxorubicin are an important subclass of polyketides. Aromatic polyketides are biosynthesized through repeated decarboxylative condensations between malonyl-CoA-derived building blocks. Their synthesis is catalyzed by type II polyketide synthases (PKSs), which share a common architecture and mechanism with type II fatty acid synthases found in bacteria and plants. A minimal type II PKS is comprised of four proteins, including the ketosynthase (KS), the chain length factor (CLF), the acyl carrier protein (ACP), and the malonyl-CoA:ACP transacylase (MAT). The KS and the CLF form a heterodimer which catalyzes condensation reactions between successive malonyl units and controls the overall polyketide chain length. The SCO1815 from Streptomyces coelicolor A3(2), an uncharacterized homologue of a NADPH-dependent ketoreductase, recognizes and reduces the beta-ketoacyl-ACP intermediate from the initiation module of the R1128 PKS. The X-ray crystal structure of SCO1815 was determined to 2.0 ¿. The structure shows that SCO1815 adopts a Rossmann fold and suggests that a conformational change occurs upon cofactor binding. We propose that a positively charged patch formed by three conserved residues is the ACP docking site. These findings provide new engineering opportunities for incorporating unnatural primer units into novel polyketides.