Institute for Organic Chemistry and BMWZ, Leibniz Universität Hannover, Schneiderberg 38, 30167, Hannover, Germany.
Structure and Function of Proteins, Helmholtz Centre for Infection Research, Inhoffenstr. 7, 38124, Braunschweig, Germany.
Angew Chem Int Ed Engl. 2021 Sep 6;60(37):20308-20312. doi: 10.1002/anie.202106718. Epub 2021 Aug 11.
The non-canonical terpene cyclase AsR6 is responsible for the formation of 2E,6E,9E-humulene during the biosynthesis of the tropolone sesquiterpenoid (TS) xenovulene A. The structures of unliganded AsR6 and of AsR6 in complex with an in crystallo cyclized reaction product and thiolodiphosphate reveal a new farnesyl diphosphate binding motif that comprises a unique binuclear Mg -cluster and an essential K289 residue that is conserved in all humulene synthases involved in TS formation. Structure-based site-directed mutagenesis of AsR6 and its homologue EupR3 identify a single residue, L285/M261, that controls the production of either 2E,6E,9E- or 2Z,6E,9E-humulene. A possible mechanism for the observed stereoselectivity was investigated using different isoprenoid precursors and results demonstrate that M261 has gatekeeping control over product formation.
非规范萜烯环化酶 AsR6 负责在 tropolone 倍半萜（TS） xenovulene A 的生物合成过程中形成 2E,6E,9E-葎草烯。未配位的 AsR6 及其与晶体中环化反应产物和硫代二磷酸形成的复合物的结构揭示了一个新的法呢基二磷酸结合基序，它包含一个独特的双核 Mg-簇和一个在所有涉及 TS 形成的葎草烯合酶中保守的必需 K289 残基。基于结构的 AsR6 及其同源物 EupR3 的定点突变鉴定出一个单一残基 L285/M261，它控制着 2E,6E,9E-或 2Z,6E,9E-葎草烯的产生。使用不同的异戊烯前体研究了观察到的立体选择性的可能机制，结果表明 M261 对产物形成具有门控控制。
