6月7日,，Structure雜志在線報道了Atg12-Atg5偶聯(lián)的結(jié)構(gòu)基礎,。為深入理解自噬這一重要的生命現(xiàn)象，提供了新的重要信息,。
Atg12-Atg5偶聯(lián),，由一種泛素樣偶聯(lián)系統(tǒng)形成，對自噬復合體的形成具有關鍵作用,。但Atg12-Atg5偶聯(lián)形成的分子機制一直不明,。
該研究解析了一種耐熱酵母,，克魯維酵母菌屬（Km）的Atg10和Atg5同源體。Km Atg10包含一個帶有特征性附件的E2核心折疊,，包括兩個β鏈,。而Km Atg5帶有兩個泛素樣結(jié)構(gòu)域和一個螺旋結(jié)構(gòu)域。
核磁共振實驗,、突變分析以及交聯(lián)實驗顯示Km Atg10通過其特征性β鏈,，直接識別Km Atg5，特別是其C-末端的泛素樣結(jié)構(gòu)域,。動力學分析提示,，Km Atg10的Tyr56和Asn114可將Km Atg5Lys145的側(cè)鏈置于與Atg12發(fā)生偶聯(lián)反應的最佳取向。這樣的結(jié)構(gòu)特征使Atg10在無需特異性E3酶的條件下,，介導Atg12-Atg5偶聯(lián)的形成,。（生物谷bioon.com)
doi:10.1016/j.cell.2011.10.017
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Structural Insights into Atg10-Mediated Formation of the Autophagy-Essential Atg12-Atg5 Conjugate
Masaya Yamaguchi, Nobuo N. Noda, Hayashi Yamamoto, Takayuki Shima, Hiroyuki Kumeta, Yoshihiro Kobashigawa, Rinji Akada
The Atg12-Atg5 conjugate, which is formed by an ubiquitin-like conjugation system, is essential to autophagosome formation, a central event in autophagy. Despite its importance, the molecular mechanism of the Atg12-Atg5 conjugate formation has not been elucidated. Here, we report the solution and crystal structures of Atg10 and Atg5 homologs from Kluyveromyces marxianus (Km), a thermotolerant yeast. KmAtg10 comprises an E2-core fold with characteristic accessories, including two β strands, whereas KmAtg5 has two ubiquitin-like domains and a helical domain. The nuclear magnetic resonance experiments, mutational analyses, and crosslinking experiments showed that KmAtg10 directly recognizes KmAtg5, especially its C-terminal ubiquitin-like domain, by its characteristic two β strands. Kinetic analysis suggests that Tyr56 and Asn114 of KmAtg10 may place the side chain of KmAtg5 Lys145 into the optimal orientation for its conjugation reaction with Atg12. These structural features enable Atg10 to mediate the formation of the Atg12-Atg5 conjugate without a specific E3 enzyme.
