期刊
PLANT COMMUNICATIONS
卷 1, 期 5, 页码 -出版社
ELSEVIER
DOI: 10.1016/j.xplc.2020.100051
关键词
terpenoid; terpene synthase; sesterterpene; cyclization mechanism; crystal structure
资金
- National Key R&D Program of China [2018YFA0900600]
- National Natural Science Foundation of China [31970315, 31700263]
- ``Priority Research Program'' of the Chinese Academy of Sciences [ZDRW-ZS2019-2, XDB27020103]
- MEXT, Japan (JSPS KAKENHI) [JP16H06443]
- State Key Laboratory of Plant Genomics of China [SKLPG2016A-13]
- Foundation of Youth Innovation Promotion Association of the Chinese Academy of Sciences
Class I terpene synthase (TPS) generates bioactive terpenoids with diverse backbones. Sesterterpene synthase (sester-TPS, C25), a branch of class I TPSs, was recently identified in Brassicaceae. However, the catalytic mechanisms of sester-TPSs are not fully understood. Here, we first identified three nonclustered functional sester-TPSs (AtTPS06, AtTPS22, and AtTPS29) in Arabidopsis thaliana. AtTPS06 utilizes a type-B cyclization mechanism, whereas most other sester-TPSs produce various sesterterpene back-bones via a type- A cyclization mechanism. We then determined the crystal structure of the AtTPS18-FSPP complex to explore the cyclization mechanism of plant sester-TPSs. We used structural comparisons and site-directed mutagenesis to further elucidate the mechanism: (1) mainly due to the outward shift of helix G, plant sester-TPSs have a larger catalytic pocket than do mono-, sesqui-, and di-TPSs to accommodate GFPP; (2) type-A sester-TPSs have more aromatic residues (five or six) in their catalytic pocket than classic TPSs (two or three), which also determines whether the type-A or type-B cyclization mechanism is active; and (3) the other residues responsible for product fidelity are determined by interconversion of AtTPS18 and its close homologs. Altogether, this study improves our understanding of the catalytic mechanism of plant sester-TPS, which ultimately enables the rational engineering of sesterterpenoids for future applications.
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