近日，清华大学柴继杰课题组与英国东安格利亚大学Cyril Zipfel课题组合作报道了植物中RALF多肽的受体识别分子机制。这一研究成果于2019年8月8日发表在国际顶尖学术期刊《自然》上。

研究人员发现RALF23引起FER与LLG1复合物来调控免疫信号。结构和生化结果表明LLG1（其对RALF23应答在遗传上具有重要性）和相关的LLG2分别直接结合RALF23来引起RALF23LLG1FER和RALF23LLG2FER异源复合物的组装。RALF23的N端保守区域足以使其被LLG1、LLG2或LLG3进行生化识别，结合实验表明，其他有这一保守N端区域的RALF多肽也能够被LGG蛋白以相似的模式所识别。结构数据也表明，RALF23的识别由LLG1、LLG2和LLG3的构象灵活的C端侧面所实现。他们的工作揭示了植物中与受体激酶一起工作的GPI锚定蛋白识别多肽的机制。这为了解不同RALF多肽，通过被CrRLK1L受体激酶与LRE和LGG家族的GPI锚定蛋白形成异源复合物所识别后，如何调控多个生理过程提供了分子框架。

研究人员表示，长春花（Catharanthus roseus）RLK1-like（CrRLK1L）家族的受体激酶已成为植物繁殖、生长和环境响应的重要调控者。内源性快速碱化因子（RAPID ALKALINIZATION FACTOR，RALF）多肽被认为是CrRLK1L家族多个成员的配体。然而，这种识别的分子机制是未知的。

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柴继杰，清华大学研究员、博士生导师。其实验室关注并研究在生物学及药学应用中的重要大分子结构与功能。在本项研究中，课题组有别于过去研究发现的受体激酶基于同型二聚或多聚来识别配体的传统模式，揭示了受体激酶与膜锚定蛋白形成异型复合物识别配体的模式，为植物受体激酶以及膜锚定蛋白的结构功能研究提供了全新的范例。据介绍，该研究也纠正了植物Malectin也会识别多糖的认识，证明了动植物Malectin结构域在分别进化后，已获得了截然不同的配体识别功能。（据清华大学）

附：英文原文

Title: Mechanisms of RALF peptide perception by a heterotypic receptor complex

Author: Yu Xiao, Martin Stegmann, Zhifu Han, Thomas A. DeFalco, Katarzyna Parys, Li Xu, Youssef Belkhadir, Cyril Zipfel, Jijie Chai

Issue&Volume: Volume 572 Issue 7768

Abstract: Receptor kinases of the Catharanthus roseus RLK1-like (CrRLK1L) family have emerged as important regulators of plant reproduction, growth and responses to the environment. Endogenous RAPID ALKALINIZATION FACTOR (RALF) peptides have previously been proposed as ligands for several members of the CrRLK1L family. However, the mechanistic basis of this perception is unknown. Here we report that RALF23 induces a complex between the CrRLK1L FERONIA (FER) and LORELEI (LRE)-LIKE GLYCOSYLPHOSPHATIDYLINOSITOL (GPI)-ANCHORED PROTEIN 1 (LLG1) to regulate immune signalling. Structural and biochemical data indicate that LLG1 (which is genetically important for RALF23 responses) and the related LLG2 directly bind RALF23 to nucleate the assembly of RALF23LLG1FER and RALF23LLG2FER heterocomplexes, respectively. A conserved N-terminal region of RALF23 is sufficient for the biochemical recognition of RALF23 by LLG1, LLG2 or LLG3, and binding assays suggest that other RALF peptides that share this conserved N-terminal region may be perceived by LLG proteins in a similar manner. Structural data also show that RALF23 recognition is governed by the conformationally flexible C-terminal sides of LLG1, LLG2 and LLG3. Our work reveals a mechanism of peptide perception in plants by GPI-anchored proteins that act together with a phylogenetically unrelated receptor kinase. This provides a molecular framework for understanding how diverse RALF peptides may regulate multiple processes, through perception by distinct heterocomplexes of CrRLK1L receptor kinases and GPI-anchored proteins of the LRE and LLG family.

DOI: 10.1038/s41586-019-1409-7

Source: https://www.nature.com/articles/s41586-019-1409-7