加州理工學(xué)院研究人員利用低溫電子顯微鏡(electron cryomicroscope)首次觀察到細(xì)菌細(xì)胞中接受化學(xué)刺激的化學(xué)受體(chemoreceptors)的排列結(jié)構(gòu),。此外,，他們還發(fā)現(xiàn)這種特殊的排列結(jié)構(gòu)廣泛出現(xiàn)在所有細(xì)菌物種中,，表明該結(jié)構(gòu)在進(jìn)化上十分保守,。
這項(xiàng)研究發(fā)表在本周提前出版的Proceedings of the National Academy of Sciences雜志上,，或許有助于科學(xué)家更好地了解許多生物代謝過程中復(fù)雜的信號通路,。
鞭毛是細(xì)菌最重要的運(yùn)動結(jié)構(gòu),，細(xì)菌的運(yùn)動方向不是隨機(jī)的,，而是根據(jù)具體的環(huán)境有趨利避害的趨勢。但細(xì)菌如何分辨有利環(huán)境和不利環(huán)境呢,？研究人員發(fā)現(xiàn),，在細(xì)菌靠近鞭毛處，有一些微小的蛋白分子——化學(xué)受體,，該蛋白就像是從細(xì)菌細(xì)胞中長出的“蛋白質(zhì)天線”,，可以與外界的營養(yǎng)物質(zhì)或其他化學(xué)刺激結(jié)合，并將獲得的化學(xué)信號傳遞到細(xì)胞內(nèi),。
實(shí)驗(yàn)發(fā)現(xiàn),，這類化學(xué)受體對環(huán)境中的積極刺激或消極刺激非常敏感。研究人員認(rèn)為,，進(jìn)一步了解這些受體之間相互作用的方式十分重要,。研究人員利用低溫電子顯微鏡獲得了700張細(xì)菌完整的三維圖像，研究人員對這些快速冷凍的細(xì)菌內(nèi)部結(jié)構(gòu)進(jìn)行分析,，發(fā)現(xiàn)化學(xué)受體呈規(guī)則的重復(fù)六邊形排列,，在六邊形的每個頂點(diǎn)有一對受體與另外3個受體連接。
研究人員對13種不同的菌種進(jìn)行研究發(fā)現(xiàn),，這種特殊的化學(xué)受體排列結(jié)構(gòu)出現(xiàn)在幾乎所有的細(xì)菌中,。（生物谷Bioon.com）
生物谷推薦原始出處：
PNAS September 23, 2009, doi: 10.1073/pnas.0905181106
Universal architecture of bacterial chemoreceptor arrays
Ariane Briegela,b, Davi R. Ortegac,d, Elitza I. Tochevaa, Kristin Wuichetd, Zhuo Lia,b, Songye Chena, Axel Müllere, Cristina V. Iancua,1, Gavin E. Murphya,2, Megan J. Dobroa, Igor B. Zhulind,f and Grant J. Jensena,b,3
Divisions of aBiology and
eChemistry and
bHoward Hughes Medical Institute, California Institute of Technology, Pasadena, CA 91125;
Departments of cPhysics and
dMicrobiology, University of Tennessee, Knoxville, TN 37996; and
fBioEnergy Center and Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831Chemoreceptors are key components of the high-performance signal transduction system that controls bacterial chemotaxis. Chemoreceptors are typically localized in a cluster at the cell pole, where interactions among the receptors in the cluster are thought to contribute to the high sensitivity, wide dynamic range, and precise adaptation of the signaling system. Previous structural and genomic studies have produced conflicting models, however, for the arrangement of the chemoreceptors in the clusters. Using whole-cell electron cryo-tomography, here we show that chemoreceptors of different classes and in many different species representing several major bacterial phyla are all arranged into a highly conserved, 12-nm hexagonal array consistent with the proposed “trimer of dimers” organization. The various observed lengths of the receptors confirm current models for the methylation, flexible bundle, signaling, and linker sub-domains in vivo. Our results suggest that the basic mechanism and function of receptor clustering is universal among bacterial species and was thus conserved during evolution.
