Annaval Thibault, Rudolf Jeffrey D, Chang Chin-Yuan, Lohman Jeremy R, Kim Youngchang, Bigelow Lance, Jedrzejczak Robert, Babnigg Gyorgy, Joachimiak Andrzej, Phillips George N, Shen Ben
Department of Chemistry, Department of Molecular Medicine, and Natural Products Library Initiative at The Scripps Research Institute, The Scripps Research Institute, 130 Scripps Way, Jupiter, Florida 33458, United States.
Midwest Center for Structural Genomics and Structural Biology Center, Biosciences Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, United States.
ACS Omega. 2017 Aug 31;2(8):5159-5169. doi: 10.1021/acsomega.7b00933. Epub 2017 Aug 30.
Enediynes are potent natural product anticancer antibiotics, and are classified as 9- or 10-membered according to the size of their enediyne core carbon skeleton. Both 9- and 10-membered enediyne cores are biosynthesized by the enediyne polyketide synthase (PKSE), thioesterase (TE), and PKSE-associated enzymes. Although the divergence between 9- and 10-membered enediyne core biosynthesis remains unclear, it has been observed that nascent polyketide intermediates, tethered to the acyl carrier protein (ACP) domain of PKSE, could be released by TE in the absence of the PKSE-associated enzymes. In this study, we determined the crystal structure of SgcE10, the TE that participates in the biosynthesis of the 9-membered enediyne C-1027. Structural comparison of SgcE10 with CalE7 and DynE7, two TEs that participate in the biosynthesis of the 10-membered enediynes calicheamicin and dynemicin, respectively, revealed that they share a common α/β hot-dog fold. The amino acids involved in both substrate binding and catalysis are conserved among SgcE10, CalE7, and DynE7. The volume and the shape of the substrate-binding channel and active site in SgcE10, CalE7, and DynE7 confirm that TEs from both 9- and 10-membered enediyne biosynthetic machineries bind the linear form of similar ACP-tethered polyene intermediates. Taken together, these findings further support the proposal that the divergence between 9- and 10-membered enediyne core biosynthesis occurs beyond PKSE and TE catalysis.
烯二炔是一类具有强大抗癌活性的天然抗生素，根据其烯二炔核心碳骨架的大小可分为9元或10元烯二炔。9元和10元烯二炔核心均由烯二炔聚酮合酶（PKSE）、硫酯酶（TE）以及与PKSE相关的酶进行生物合成。尽管9元和10元烯二炔核心生物合成之间的差异尚不清楚，但据观察，在没有与PKSE相关的酶的情况下，连接在PKSE酰基载体蛋白（ACP）结构域上的新生聚酮中间体可被TE释放。在本研究中，我们确定了参与9元烯二炔C-1027生物合成的硫酯酶SgcE10的晶体结构。将SgcE10与分别参与10元烯二炔加利车霉素和力达霉素生物合成的两种硫酯酶CalE7和DynE7进行结构比较，发现它们具有共同的α/β热狗折叠结构。在SgcE10、CalE7和DynE7中，参与底物结合和催化的氨基酸是保守的。SgcE10、CalE7和DynE7中底物结合通道和活性位点的体积与形状证实，来自9元和10元烯二炔生物合成机制的硫酯酶均可结合类似的与ACP相连的线性多烯中间体。综上所述，这些发现进一步支持了9元和10元烯二炔核心生物合成之间的差异发生在PKSE和TE催化之后这一观点。
