AT-less Type I Polyketide Synthases

描述(申请人提供)：在美国，每4例死亡中就有1例死于癌症。因此，开发全新的、临床有用的抗癌药物构成了国家健康和研究的当务之急。雷诺霉素(LNM)、异米非司他丁(iso-MGS)、米非司他丁(MGS)和拉米霉素(LTM)是一类具有广泛应用前景的新型抗癌药物。一个巨大的挑战是开发方法来制备这些复杂的天然产物及其结构类似物，用于机械研究和临床开发。在这项竞争性更新申请中，我们建议(I)继续研究LNM、iso-MGS和LTM的生物合成，以发现新的化学和酶学；(Ii)将组合生物合成方法应用于LNM、iso-MGS和LTM的生物合成机械，以生产新型抗癌药物。我们的假设是：(I)LNM、iso-MGS和LTM无AT的I型PKS代表了一种新的PKS结构，其研究将揭示PKS催化的分子机制；(Ii)无AT的I型PKS为PKS工程提供了新的机会，通过组合生物合成扩大聚酮结构多样性的方法和策略；(Iii)LNM、iso-MGS和LTM生物合成的其他几个方面是前所未有的，其表征将揭示新的化学和酶学；以及(Iv)LNM、iso-MGS、MGS和LTM是具有新颖作用模式的优秀抗癌先导这些天然产物及其结构类似物有可能被实际开发成新的抗癌药物。本授权期的具体目标是：(I)以LNM、iso-MGS和LTM无AT-I型PKS为模型，研究无AT的I型PKS如何与其同源酰基转移酶(AT)相互作用，构成聚酮生物合成的功能性PKS巨合酶；(Ii)LNM、iso-MGS和LTM生物合成的新酶的机械和结构特征；以及(Iii)合理设计LNM、iso-MGS和LTM代谢产物过量生产和新类似物的途径。这些研究的成果包括发现和开发新的抗癌药物先导化合物和潜在的临床有用的抗癌药物。我们研究的长期目标是在分子水平上了解微生物如何合成复杂的天然产物，并将组合生物合成方法开发和应用于天然产物，以用于抗癌药物的发现和开发。

DESCRIPTION (provided by applicant): Cancer causes 1 of every 4 deaths in the US. The development of fundamentally new, clinically useful anticancer drugs therefore constitutes a national health and research imperative. Leinamycin (LNM), iso-migrastatin (iso-MGS), migrastatin (MGS), and lactimidomycin (LTM) are promising anticancer drug leads with unprecedented modes of action. A great challenge is to develop ways to prepare these complex natural products and their structural analogs for mechanistic studies and clinical development. We propose in this Competitive Renewal application (i) to continue to study LNM, iso-MGS, and LTM biosynthesis to discover novel chemistry and enzymology and (ii) to apply combinatorial biosynthesis methods to the LNM, iso-MGS, and LTM biosynthetic machinery for production of novel anticancer drugs. Our hypotheses are (i) the LNM, iso-MGS, and LTM AT-less type I PKSs represent a novel PKS architecture, the studies of which will reveal new insights into the molecular mechanism of PKS catalysis, (ii) AT-less type I PKSs provide new opportunities for PKS engineering, methods and strategies for expanding polyketide structural diversity by combinatorial biosynthesis, (iii) several other aspects in LNM, iso-MGS, and LTM biosynthesis are unprecedented, the characterization of which will uncover new chemistry and enzymology, and (iv) LNM, iso-MGS, MGS, and LTM are excellent anticancer leads with novel modes of action, and these natural products and their structural analogs could be realistically developed into new anticancer drugs. The specific aims for this grant period are: (i) mechanistic and structural characterization of the LNM, iso-MGS, and LTM AT-less type I PKSs as models to investigate how AT-less type I PKS interacts with its cognate acyltransferase (AT) to constitute a functional PKS megasynthase for polyketide biosynthesis; (ii) mechanistic and structural characterization of novel enzymes for LNM, iso-MGS, and LTM biosynthesis; and (iii) rational engineering of the LNM, iso-MGS, and LTM pathways for metabolite overproduction and novel analogs. The outcomes of these studies include the discovery and development of novel anticancer drug leads and potentially clinically useful anticancer drugs. The long-term goal of our research is to understand at a molecular level how microorganisms synthesize complex natural products and to develop and apply combinatorial biosynthesis methods to natural products for anticancer drug discovery and development.