加州理工學院研究人員利用低溫電子顯微鏡(electron cryomicroscope)首次觀察到細菌細胞中接受化學刺激的化學受體(chemoreceptors)的排列結構,。此外,，他們還發(fā)現(xiàn)這種特殊的排列結構廣泛出現(xiàn)在所有細菌物種中,，表明該結構在進化上十分保守,。
這項研究發(fā)表在本周提前出版的Proceedings of the National Academy of Sciences雜志上,，或許有助于科學家更好地了解許多生物代謝過程中復雜的信號通路,。
鞭毛是細菌最重要的運動結構,，細菌的運動方向不是隨機的，而是根據(jù)具體的環(huán)境有趨利避害的趨勢,。但細菌如何分辨有利環(huán)境和不利環(huán)境呢,？研究人員發(fā)現(xiàn)，在細菌靠近鞭毛處,，有一些微小的蛋白分子——化學受體,，該蛋白就像是從細菌細胞中長出的“蛋白質天線”，可以與外界的營養(yǎng)物質或其他化學刺激結合,，并將獲得的化學信號傳遞到細胞內(nèi),。
實驗發(fā)現(xiàn)，這類化學受體對環(huán)境中的積極刺激或消極刺激非常敏感,。研究人員認為,，進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張細菌完整的三維圖像,，研究人員對這些快速冷凍的細菌內(nèi)部結構進行分析,，發(fā)現(xiàn)化學受體呈規(guī)則的重復六邊形排列，在六邊形的每個頂點有一對受體與另外3個受體連接,。
研究人員對13種不同的菌種進行研究發(fā)現(xiàn),，這種特殊的化學受體排列結構出現(xiàn)在幾乎所有的細菌中。（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.
