当前位置: X-MOL 学术Science › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Organometallic and radical intermediates reveal mechanism of diphthamide biosynthesis
Science ( IF 56.9 ) Pub Date : 2018-03-15 , DOI: 10.1126/science.aao6595
Min Dong 1 , Venkatesan Kathiresan 2 , Michael K. Fenwick 1 , Andrew T. Torelli 1 , Yang Zhang 1 , Jonathan D. Caranto 1 , Boris Dzikovski 1 , Ajay Sharma 2 , Kyle M. Lancaster 1 , Jack H. Freed 1 , Steven E. Ealick 1 , Brian M. Hoffman 2 , Hening Lin 1, 3
Affiliation  

A quick freeze shows an enzyme's secrets Organic radicals are chemically useful in enzymatic reactions but are often hard to observe, owing to their short lifetimes. Dong et al. used rapid freeze-quench methods to trap two intermediates formed by a noncanonical radical S-adenosylmethionine (SAM) enzyme: a fragmented SAM molecule bound to the iron-sulfur cluster through an iron-carbon bond and a product-like radical. The structure of the SAM-bound enzyme reveals a noncolinear arrangement of carbon, sulfur, and iron atoms. The arrangement of bonds suggests that the organometallic intermediate may be created through a two-electron nucleophilic mechanism. A subsequent radical intermediate is formed on the protein substrate and resolves by oxidation to form the amino acid product diphthamide. Science, this issue p. 1247 An unusual radical enzyme forms an iron-carbon bond as the first step in the modification of a protein side chain. Diphthamide biosynthesis involves a carbon-carbon bond-forming reaction catalyzed by a radical S-adenosylmethionine (SAM) enzyme that cleaves a carbon-sulfur (C–S) bond in SAM to generate a 3-amino-3-carboxypropyl (ACP) radical. Using rapid freezing, we have captured an organometallic intermediate with an iron-carbon (Fe–C) bond between ACP and the enzyme’s [4Fe-4S] cluster. In the presence of the substrate protein, elongation factor 2, this intermediate converts to an organic radical, formed by addition of the ACP radical to a histidine side chain. Crystal structures of archaeal diphthamide biosynthetic radical SAM enzymes reveal that the carbon of the SAM C–S bond being cleaved is positioned near the unique cluster Fe, able to react with the cluster. Our results explain how selective C–S bond cleavage is achieved in this radical SAM enzyme.

中文翻译:

有机金属和自由基中间体揭示了双邻苯二甲胺生物合成的机制

快速冷冻显示酶的秘密 有机自由基在酶促反应中具有化学作用,但由于其寿命很短,通常很难观察到。董等人。使用快速冷冻淬灭方法捕获由非经典自由基 S-腺苷甲硫氨酸 (SAM) 酶形成的两种中间体:通过铁碳键和产物样自由基与铁硫簇结合的碎片化 SAM 分子。SAM 结合酶的结构揭示了碳、硫和铁原子的非共线排列。键的排列表明有机金属中间体可以通过双电子亲核机制产生。随后在蛋白质底物上形成自由基中间体,并通过氧化分解形成氨基酸产物二苯甲酰胺。科学,这个问题 p。1247 一种不寻常的自由基酶形成铁碳键,作为蛋白质侧链修饰的第一步。Diphthamide 生物合成涉及由自由基 S-腺苷甲硫氨酸 (SAM) 酶催化的碳-碳键形成反应,该酶裂解 SAM 中的碳-硫 (C-S) 键以生成 3-氨基-3-羧丙基 (ACP) 自由基. 使用快速冷冻,我们捕获了在 ACP 和酶的 [4Fe-4S] 簇之间具有铁碳 (Fe-C) 键的有机金属中间体。在底物蛋白、延伸因子 2 存在下,该中间体转化为有机自由基,通过将 ACP 自由基添加到组氨酸侧链而形成。古菌二苯甲酰胺生物合成自由基 SAM 酶的晶体结构表明,被裂解的 SAM C-S 键的碳位于独特的簇 Fe 附近,能够与集群做出反应。我们的结果解释了如何在这种自由基 SAM 酶中实现选择性 C-S 键裂解。
更新日期:2018-03-15
down
wechat
bug