Structures of D14 and D14L in the strigolactone and karrikin signaling pathways
Structures of D14 and D14L in the strigolactone and karrikin signaling pathways
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DOI：
10.1111/gtc.12025
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发表时间：
2013-02-01
期刊：
影响因子：
2.1
通讯作者：
Hakoshima, Toshio
中科院分区：
文献类型：
--
作者：
Kagiyama, Megumi;Hirano, Yoshinori;Hakoshima, Toshio
独脚金内酯 (SL) 是抑制枝条分枝的植物激素。 DWARF14 (D14) 抑制水稻分蘖，是分枝抑制途径中的 SL 受体候选者，而密切同源物 DWARF14-LIKE (D14L) 参与 karrikins (KAR) 信号传导途径，KAR 源自烧焦的植被，作为种子发芽的烟雾刺激剂。我们提供了生物活性 SL 类似物 GR24 与 D14 直接结合的第一个证据。等温滴定量热法测量显示 D14GR24 结合亲和力在亚微摩尔范围内。同样，生物活性 KAR1 在微摩尔范围内直接结合 D14L。水稻 D14 的晶体结构显示出紧凑的 α/β 折叠水解酶结构域，形成能够容纳 GR24 的深层配体结合口袋。尽管口袋对溶剂开放，但在β6链和αD螺旋之间插入四个α螺旋形成口袋的螺旋帽。该口袋包含与氧阴离子孔对齐的保守催化三联体 Ser-His-Asp，表明水解酶活性。尽管这些结构特征在 D14L 中得到了保留，但 D14L 的型腔比 D14 的型腔要小。 KAR 不敏感突变 kai2-1 位于突出的长 β 6-aD1 环，这是 D14 和 D14L 的特征，但在相关的 α/β 折叠水解酶中则不然。
Strigolactones (SLs) are plant hormones that inhibit shoot branching. DWARF14 (D14) inhibits rice tillering and is an SL receptor candidate in the branching inhibition pathway, whereas the close homologue DWARF14-LIKE (D14L) participates in the signaling pathway of karrikins (KARs), which are derived from burnt vegetation as smoke stimulants of seed germination. We provide the first evidence for direct binding of the bioactive SL analogue GR24 to D14. Isothermal titration calorimetry measurements show a D14GR24 binding affinity in the sub-micromolar range. Similarly, bioactive KAR1 directly binds D14L in the micromolar range. The crystal structure of rice D14 shows a compact a-/beta-fold hydrolase domain forming a deep ligand-binding pocket capable of accommodating GR24. Insertion of four a-helices between beta 6 strand and aD helix forms the helical cap of the pocket, although the pocket is open to the solvent. The pocket contains the conserved catalytic triad Ser-His-Asp aligned with the oxyanion hole, suggesting hydrolase activity. Although these structural characteristics are conserved in D14L, the D14L pocket is smaller than that of D14. The KAR-insensitive mutation kai2-1 is located at the prominent long beta 6-aD1 loop, which is characteristic in D14 and D14L, but not in related a-/beta-fold hydrolases.