3月2日,，清華大學(xué)生命科學(xué)院施一公教授領(lǐng)導(dǎo)的研究組與王佳偉副教授合作在《自然》在線發(fā)表論文,，報(bào)道原核細(xì)胞蛋白酶體調(diào)節(jié)亞基MecA-ClpC異六聚體結(jié)構(gòu)與功能的研究,。
ATP依賴的可調(diào)控蛋白質(zhì)水解廣泛存在于大多數(shù)生命體中,，對(duì)于及時(shí)清除機(jī)體內(nèi)的垃圾蛋白以及調(diào)節(jié)蛋白具有十分重要的作用,。原核生物中負(fù)責(zé)這一功能的蛋白酶體由調(diào)節(jié)亞基-Clp/Hsp100家族成員同催化亞基ClpP兩部分組成,。研究發(fā)現(xiàn)，Clp/Hsp100家族蛋白都是以六聚體形式執(zhí)行功能,。ClpC是Clp/Hsp100家族的重要成員,，含有兩個(gè)AAA+(ATPasesassociatedwithdiversecellularactivities)結(jié)構(gòu)域（核酸結(jié)合結(jié)構(gòu)域），與該家族其它成員不同的是,，ClpC的六聚體形成及其進(jìn)一步的激活需要接頭蛋白MecA的參與,。利用ATP水解的能量，激活后的六聚體MecA-ClpC分子能夠去折疊特異性蛋白質(zhì)底物,，并將生成的去折疊多肽鏈轉(zhuǎn)運(yùn)到ClpP中降解,。但是，MecA如何介導(dǎo)ClpC形成六聚體并激活ClpC的分子機(jī)制一直都沒(méi)有明確的解釋,。
自2007年6月起,，施一公教授領(lǐng)導(dǎo)的該課題組一直致力于對(duì)原核細(xì)胞內(nèi)蛋白酶體調(diào)控機(jī)理的研究。經(jīng)過(guò)3年多的艱辛努力,，該課題組首次解析了枯草芽孢桿菌內(nèi)蛋白酶體調(diào)節(jié)亞基MecA-ClpC復(fù)合物的三個(gè)相關(guān)晶體結(jié)構(gòu),，并結(jié)合大量的生化實(shí)驗(yàn)數(shù)據(jù),，揭示了六聚體MecA-ClpC復(fù)合物的組裝方式，闡明了MecA介導(dǎo)ClpC激活的分子機(jī)理,，并提供了MecA-ClpC執(zhí)行功能的結(jié)構(gòu)基礎(chǔ),。這些發(fā)現(xiàn)對(duì)揭密其它Clp/Hsp100分子機(jī)器的組裝方式也有很好的借鑒作用，并且為研究真核生物內(nèi)更為復(fù)雜的泛素－蛋白酶體系統(tǒng)提供了方法論和實(shí)驗(yàn)基礎(chǔ),。（生物谷Bioon.com）
生物谷推薦原文出處：
Nature doi:10.1038/nature09780
Structure and mechanism of the hexameric MecA–ClpC molecular machine
Feng Wang,1, 2 Ziqing Mei,1, 2 Yutao Qi,1 Chuangye Yan,1 Qi Hu,1 Jiawei Wang1 & Yigong Shi1
Regulated proteolysis by ATP-dependent proteases is universal in all living cells. Bacterial ClpC, a member of the Clp/Hsp100 family of AAA+ proteins (ATPases associated with diverse cellular activities) with two nucleotide-binding domains (D1 and D2), requires the adaptor protein MecA for activation and substrate targeting. The activated, hexameric MecA–ClpC molecular machine harnesses the energy of ATP binding and hydrolysis to unfold specific substrate proteins and translocate the unfolded polypeptide to the ClpP protease for degradation. Here we report three related crystal structures: a heterodimer between MecA and the amino domain of ClpC, a heterododecamer between MecA and D2-deleted ClpC, and a hexameric complex between MecA and full-length ClpC. In conjunction with biochemical analyses, these structures reveal the organizational principles behind the hexameric MecA–ClpC complex, explain the molecular mechanisms for MecA-mediated ClpC activation and provide mechanistic insights into the function of the MecA–ClpC molecular machine. These findings have implications for related Clp/Hsp100 molecular machines.
