The x-ray crystal structure of recombinant trichodiene synthase from
Fusarium sporotrichioides
has been determined to 2.5-Å resolution, both unliganded and complexed with inorganic pyrophosphate. This reaction product coordinates to three Mg
2+
ions near the mouth of the active site cleft. A comparison of the liganded and unliganded structures reveals a ligand-induced conformational change that closes the mouth of the active site cleft. Binding of the substrate farnesyl diphosphate similarly may trigger this conformational change, which would facilitate catalysis by protecting reactive carbocationic intermediates in the cyclization cascade. Trichodiene synthase also shares significant structural similarity with other sesquiterpene synthases despite a lack of significant sequence identity. This similarity indicates divergence from a common ancestor early in the evolution of terpene biosynthesis.
重组三烯合酶(trichodiene synthase)来自斑点孢镰刀菌(Fusarium sporotrichioides),其x-射线晶体结构已被测定至2.5埃分辨率,包括未配体和配有无机焦磷酸盐的结构。这个反应产物与活性位点裂口口附近的三个Mg2+离子配位。配有配体和未配体结构的比较揭示了配体诱导的构象变化,使活性位点裂口关闭。底物法尼基二磷酸的结合同样可能引发这种构象变化,这将通过保护环化级联反应中的反应性碳阳离子中间体来促进催化。尽管没有显著的序列同源性,三烯合酶与其他倍半萜合酶具有显著的结构相似性。这种相似性表明,倍半萜生物合成的早期进化中存在从共同祖先的分歧。