清華大學(xué)生命科學(xué)學(xué)院施一公教授領(lǐng)導(dǎo)的研究組合作解析了甲酸（formate）通道FocA的高分辨率結(jié)構(gòu),，研究結(jié)果11月25日以Article的形式發(fā)表于Nature,。
甲酸是細(xì)菌在無(wú)氧呼吸條件下的主要代謝產(chǎn)物之一,，發(fā)酵狀態(tài)下,，細(xì)菌體內(nèi)積聚了大量的甲酸需要穿過(guò)內(nèi)膜進(jìn)一步代謝,。甲酸同時(shí)還是古老微生物的重要碳源之一,。盡管甲酸可以透過(guò)細(xì)胞內(nèi)膜,，但是大量甲酸的快速運(yùn)輸需要轉(zhuǎn)運(yùn)系統(tǒng),。FocA是在1994年被發(fā)現(xiàn)的甲酸轉(zhuǎn)運(yùn)蛋白,，屬于FNT家族，可以轉(zhuǎn)運(yùn)甲酸,、亞硝酸等短鏈酸,。FNT家族一直以來(lái)被認(rèn)為是轉(zhuǎn)運(yùn)蛋白(transporter),。
施一公教授研究組歷時(shí)兩年成功解析了FocA的高分辨率原子結(jié)構(gòu)，證明FocA是通道蛋白（channel）,，而非轉(zhuǎn)運(yùn)蛋白（transporter）,。更為有趣的是，盡管FocA在氨基酸序列上與水通道蛋白（aquaporin）沒(méi)有任何相似性,，也不具備水通道的標(biāo)志性序列,，但是其結(jié)構(gòu)高度相似。不同的是,，所有已知的aquaporin蛋白都是四聚體,，而FocA以梅花狀的五聚體形式存在，并且不能夠通透水分子,。這是首次發(fā)現(xiàn)與水通道結(jié)構(gòu)類似但沒(méi)有序列同源性的其他家族蛋白,。這一發(fā)現(xiàn)對(duì)于研究膜蛋白的進(jìn)化提供了進(jìn)一步的線索。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature 462, 467-472 (26 November 2009) | doi:10.1038/nature08610
Structure of the formate transporter FocA reveals a pentameric aquaporin-like channel
Yi Wang1,4, Yongjian Huang2,4, Jiawei Wang2,4, Chao Cheng2, Weijiao Huang2, Peilong Lu1, Ya-Nan Xu3, Pengye Wang3, Nieng Yan2 & Yigong Shi1
1 Ministry of Education Protein Science Laboratory,
2 State Key Laboratory of Biomembrane and Membrane Biotechnology, Center for Structural Biology, School of Life Sciences and School of Medicine, Tsinghua University, Beijing 100084, China
3 Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
4 These authors contributed equally to this work.
Correspondence to: Nieng Yan2Yigong Shi1 Correspondence and requests for materials should be addressed to N.Y. or Y.S.
FocA is a representative member of the formate–nitrite transporter family, which transports short-chain acids in bacteria, archaea, fungi, algae and parasites. The structure and transport mechanism of the formate–nitrite transporter family remain unknown. Here we report the crystal structure of Escherichia coli FocA at 2.25 ? resolution. FocA forms a symmetric pentamer, with each protomer consisting of six transmembrane segments. Despite a lack of sequence homology, the overall structure of the FocA protomer closely resembles that of aquaporin and strongly argues that FocA is a channel, rather than a transporter. Structural analysis identifies potentially important channel residues, defines the channel path and reveals two constriction sites. Unlike aquaporin, FocA is impermeable to water but allows the passage of formate. A structural and biochemical investigation provides mechanistic insights into the channel activity of FocA.
