生物谷報道：來自美國華盛頓大學(xué)醫(yī)學(xué)院藥理學(xué)系,，印第安納州大學(xué)生物學(xué)系，英國劍橋大學(xué)化學(xué)系的研究人員鄭寧獲得了擬南芥TIR1–ASK1復(fù)合物的晶體結(jié)構(gòu),，從而建立了一種植物激素受體的第一個結(jié)構(gòu)模型，這一研究成果公布在本期（4月5日）《Nature》雜志封面上,。
部分英文原文：
Nature 446, 640-645 (5 April 2007) | doi:10.1038/nature05731; Received 27 January 2007; Accepted 8 March 2007
Mechanism of auxin perception by the TIR1 ubiquitin ligase
Xu Tan1, Luz Irina A. Calderon-Villalobos2, Michal Sharon3, Changxue Zheng1, Carol V. Robinson3, Mark Estelle2 & Ning Zheng1
Department of Pharmacology, University of Washington, School of Medicine, Box 357280, Seattle, Washington 98195, USA
Department of Biology, Indiana University, Bloomington, Indiana 47405, USA
Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW, UK
Correspondence to: Ning Zheng1 Correspondence and requests for materials should be addressed to N.Z. (Email: [email protected]).
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Abstract
Auxin is a pivotal plant hormone that controls many aspects of plant growth and development. Perceived by a small family of F-box proteins including transport inhibitor response 1 (TIR1), auxin regulates gene expression by promoting SCF ubiquitin-ligase-catalysed degradation of the Aux/IAA transcription repressors, but how the TIR1 F-box protein senses and becomes activated by auxin remains unclear. Here we present the crystal structures of the Arabidopsis TIR1–ASK1 complex, free and in complexes with three different auxin compounds and an Aux/IAA substrate peptide. These structures show that the leucine-rich repeat domain of TIR1 contains an unexpected inositol hexakisphosphate co-factor and recognizes auxin and the Aux/IAA polypeptide substrate through a single surface pocket. Anchored to the base of the TIR1 pocket, auxin binds to a partially promiscuous site, which can also accommodate various auxin analogues. Docked on top of auxin, the Aux/IAA substrate peptide occupies the rest of the TIR1 pocket and completely encloses the hormone-binding site. By filling in a hydrophobic cavity at the protein interface, auxin enhances the TIR1–substrate interactions by acting as a 'molecular glue'. Our results establish the first structural model of a plant hormone receptor.
領(lǐng)導(dǎo)這一研究的是來自華盛頓大學(xué)的鄭寧（Ning Zheng,，音譯）博士，自2000年以來,，鄭博士先后在Cell,、Nature和Science等國際權(quán)威雜志上發(fā)表了多篇文章，并且有三篇文章成為雜志的封面故事進行推薦,，去年一篇有關(guān)泛素蛋白連接酶結(jié)構(gòu)生物學(xué)的文章也發(fā)表在了10月的《Nature》雜志上。
生長素是最早被發(fā)現(xiàn)的一種植物激素,。英國的查里·達爾文和他的兒子弗蘭西斯·達爾文首先利用金絲雀翳（yi）草胚芽鞘進行向光性實驗,，發(fā)現(xiàn)在單方向光照射下，胚芽鞘向光彎曲,；如果切去胚芽鞘的尖端或在尖端套上錫箔小帽,，單側(cè)光照也不會使胚芽鞘向光彎曲；如果單側(cè)光不照射胚芽鞘尖端而只向下照射胚芽鞘下部,，胚芽鞘還是會向光彎曲,。當(dāng)時，他們推測：胚芽鞘向光彎曲是由于幼苗在單側(cè)光照射下,，產(chǎn)生某種影響,，從上部傳到下部，造成背光的一側(cè)生長快,，而這種“影響”就是植物生長素Auxin,。
之后的研究證明生長素Auxin是一種關(guān)鍵的植物激素，能調(diào)控植物生長和發(fā)育的許多方面,，在對一個小家族：F-box蛋白（包括轉(zhuǎn)運抑制應(yīng)答因子1（transport inhibitor response 1,，TIR1）的研究中發(fā)現(xiàn)，生長素Auxin可以通過促進SCF對Aux/IAA轉(zhuǎn)錄抑制子的泛素連接酶（ubiquitin-ligase）催化降解,，來調(diào)控基因的表達,，但是TIR1 F-box蛋白是如何感應(yīng)，以及通過生長素Auxin激活仍然是這一領(lǐng)域的一個未知之謎。
