加州理工学院研究人员利用低温电子显微镜(electron cryomicroscope)首次观察到细菌细胞中接受化学刺激的化学受体(chemoreceptors)的排列结构。此外,他们还发现这种特殊的排列结构广泛出现在所有细菌物种中,表明该结构在进化上十分保守。
这项研究发表在本周提前出版的Proceedings of the National Academy of Sciences杂志上,或许有助于科学家更好地了解许多生物代谢过程中复杂的信号通路。
鞭毛是细菌最重要的运动结构,细菌的运动方向不是随机的,而是根据具体的环境有趋利避害的趋势。但细菌如何分辨有利环境和不利环境呢?研究人员发现,在细菌靠近鞭毛处,有一些微小的蛋白分子——化学受体,该蛋白就像是从细菌细胞中长出的“蛋白质天线”,可以与外界的营养物质或其他化学刺激结合,并将获得的化学信号传递到细胞内。
实验发现,这类化学受体对环境中的积极刺激或消极刺激非常敏感。研究人员认为,进一步了解这些受体之间相互作用的方式十分重要。研究人员利用低温电子显微镜获得了700张细菌完整的三维图像,研究人员对这些快速冷冻的细菌内部结构进行分析,发现化学受体呈规则的重复六边形排列,在六边形的每个顶点有一对受体与另外3个受体连接。
研究人员对13种不同的菌种进行研究发现,这种特殊的化学受体排列结构出现在几乎所有的细菌中。(生物谷Bioon.com)
生物谷推荐原始出处:
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.