生物谷報(bào)道：美國(guó)Baylor醫(yī)學(xué)院（BCM）的研究者最近發(fā)現(xiàn)：當(dāng)?shù)鞍缀投嗟鞍踪|(zhì)復(fù)合物處于和它們存在的自然條件類(lèi)似的環(huán)境中時(shí)，它們的組裝可能會(huì)表現(xiàn)出與在常規(guī)靜態(tài)研究條件下的活動(dòng)或動(dòng)力學(xué)上的不同,。這一結(jié)果發(fā)表于最新一期的《結(jié)構(gòu)》雜志中
Steven Ludtke博士是BCM的生化與分子生物學(xué)助理教授,，同時(shí)也是BCM國(guó)立大分子影像中心的副主管，他和BCM以及處于達(dá)拉斯的德克薩斯大學(xué)西南醫(yī)學(xué)中心的同事們?cè)谝豁?xiàng)使用冷凍電子顯微鏡技術(shù)的研究中,，發(fā)現(xiàn)一種稱(chēng)為GroEL蛋白的突變型具有動(dòng)態(tài)行為,，這種蛋白能伴隨或幫助錯(cuò)誤折疊蛋白分子折疊成能正確的形狀，以完成其細(xì)胞內(nèi)生理功能,，而錯(cuò)誤折疊蛋白往往牽涉到許多神經(jīng)變性和其他疾病,。
冷凍電子顯微鏡能幫助科學(xué)家取得非常詳細(xì)的單一分子在類(lèi)天然環(huán)境中的二維圖象，然后通過(guò)電腦和計(jì)算生物學(xué)的運(yùn)用,，可以將一系列的二維圖象重新整合成能表現(xiàn)蛋白動(dòng)力學(xué)的三維結(jié)構(gòu)模型,。當(dāng)Ludtke和他的同事們運(yùn)用這套方法研究GroEL突變體和它的姐妹蛋白GroES時(shí)，他們驚訝地觀(guān)測(cè)到：除了兩個(gè)預(yù)測(cè)中結(jié)構(gòu)之外,，還有另一個(gè)奇怪的結(jié)構(gòu),，Ludtke描述它就像充滿(mǎn)了氣的氣球，而這種膨脹結(jié)構(gòu)之前從未被觀(guān)測(cè)過(guò),。
這種膨脹結(jié)構(gòu)直接關(guān)系到蛋白的組裝功能,。更全面的看法是這是研究任何大分子在溶液中如何表現(xiàn)的有力證據(jù)。
Figure 1. Typical Cryo-Images and Representative Reference-free 2D Class Averages
(A and B) Raw images collected on a Gatan 4k × 4k CCD on a JEOL 2010F electron cryomicroscope (scale bar is 200 Å). The white arrows indicate two particles disassociated from GroES. Both images are the farther-from-focus images from a focal pair and are 4 μm under focus. (A) The substrate-free SR398-GroES-Mg-ATP complex. (B) The SR398-αβ-GroES-Mg-ATP complex.
(C and D) Representative reference-free 2D class averages generated from the full set of SR398-GroES-Mg-ATP and SR398-αβ-GroES-Mg-ATP images, respectively (31,163 and 24,162 particles respectively). In each case 300 class averages were generated, a representative subset of which is shown. The number of particles in each class average ranges from 50 to 150. The first row contains views near the symmetric axis. The second row contains various intermediate tilts. The third row shows side views of particles disassociated from GroES. The 4th and 5th rows contain side views of GroES-associated particles. In both sets, the side views exhibit a clear axial protrusion from the base of the structure, as indicated by the white arrows. There is substantial heterogeneity in the substrate-bound case, so additional representative class averages are shown.
原文出處：
Structure November, 2006: 14 (11) 1711－1722
An Expanded Conformation of Single-Ring GroEL-GroES Complex Encapsulates an 86 kDa Substrate
Dong-Hua Chen, Jiu-Li Song, David T. Chuang, Wah Chiu, and Steven J. Ludtke
[Summary] [Full Text] [PDF] [Supplemental Data]
Articles that cite this article：
Single-Ring GroEL: An Expanded View
Sharon Grayer Wolf
Structure, 2006, 14:11:1599-1600
[Summary] [Full Text] [PDF]
作者簡(jiǎn)介：
Steven J. Ludtke
Asst. Professor of Biochemistry and Molecular Biology and Co-director of the National Center for Macromolecular Imaging at Baylor College of Medicine (not affiliated with Baylor University) Grad. School: Rice University, PhD in Physics 1996 Undergrad: Caltech (Lloyd House), graduated 1990 Check my curriculum vitae for more.
I also have a personal home page
My work involves the 3D reconstruction of molecules and macromolecules using a technique called single particle reconstruction. My most significant contribution to the field is the development of the EMAN software suite, which performs semi-automated processing of electron cryomicrographs to produce accurate 3D reconstructions at subnanometer resolutions. In this technique, a solution containing large molecules and macromolecular assemblies is vitrified (frozen in non-crystalline ice) on an electron microscope grid. It is then imaged at liquid helium or liquid nitrogen temperatures on a transmission electron microscope. Images of individual molecules/assemblies are then collected. These images are very noisy, but represent the solution-like structure of the molecule under study. A large number (1000-100,000) of these particles are then processed using a series of algorithms (implemented in EMAN) to produce accurate volumetric reconstructions of the molecule at resolutions now approaching 0.5 nm (slightly worse than atomic resolution). This technique can also be applied to heterogeneous specimens, such as those existing in multiple functional states.
A growing number of labs around the world are now equipped to collect data using this technique. The NCMI, as an NCRR funded center, participates in both collaborative and service projects using its 4 state of the art electron cryomicroscopes. Visit the NCMI home page if you are interested in performing an experiment using our facilities.
Publications：
CryoEM Related
Jiang W, Ludtke SJ. (2005) Electron cryomicroscopy of single particles at subnanometer resolution. Curr Opin Struct Biol. Ludtke, S.J., Serysheva, I.I., Hamilton, S.L. and Chiu, W. (2005) The pore structure of the closed RyR1 channel. Structure. 8:1203-11. Sitharaman, B., Kissell, K.R., Hartman, K.B., Tran, L.A., Baikalov, A., Rusakova, I., Sun, Y., Khant, H.A., Ludtke, S.J., Chiu, W., Laus, S., Toth, E., Helm, L., Merbach, A.E. and Wilson, L.J.. (2005) Superparamagnetic gadonanotubes are high-performance MRI contrast agents. Chem. Commun. 31:3915-7. Menetret, J.F., Hegde, R.S., Heinrich, S.U., Chandramouli, P., Ludtke, S.J., Rapoport, T.A., and Akey, C.W. (2005). Architecture of the ribosome-channel complex derived from native membranes. J. Mol. Biol. 348,445-57. Serysheva, I.I, Hamilton, S.L., Chiu, W., Ludtke, S.J. (2005). Structure of Ca2+ Release Channel at 14 Å Resolution. J. Mol. Biol., 345, 427-431. Zhu, Y., Carragher, B., Glaeser, R.M., Fellmann, D., Bajaj, C., Bern, M., Mouche, F., de Haas, F., Hall, R.J., Kriegman, D.J., Ludtke, S.J., Mallick, S.P., Penczek, P.A., Roseman, A.M., Sigworth, F.J., Volkmann, N., and Potter, C.S. (2004). Automatic particle selection: results of a comparative study. J Struct Biol 145, 3-14. Mao, Y., Vyas, N.K., Vyas, M.N., Chen, D.H., Ludtke, S.J., Chiu, W., and Quiocho, F.A. (2004). Structure of the bifunctional and Golgi-associated formiminotransferase cyclodeaminase octamer. Embo J 23, 2963-2971. Ludtke, S.J., Chen, D.H., Song, J.L., Chuang, D.T., and Chiu, W. (2004). Seeing GroEL at 6 A resolution by single particle electron cryomicroscopy. Structure (Camb) 12, 1129-1136. Chen, C., Ko, Y., Delannoy, M., Ludtke, S.J., Chiu, W., and , P.L. Pedersen (2004). Mitochondrial ATP synthasome: three-dimensional structure by electron microscopy of the ATP synthase in complex formation with carriers for Pi and ADP/ATP. J Biol Chem 279, 31761-31768. Brink, J., Ludtke, S.J., Kong, Y., Wakil, S.J., Ma, J., and Chiu, W. (2004). Experimental verification of conformational variation of human fatty acid synthase as predicted by normal mode analysis. Structure (Camb) 12, 185-191. Booth, C.R., Jiang, W., Baker, M.L., Zhou, Z.H., Ludtke, S.J., and Chiu, W. (2004). A 9 angstroms single particle reconstruction from CCD captured images on a 200 kV electron cryomicroscope. J Struct Biol 147, 116-127. Serysheva, II, Bare, D.J., Ludtke, S.J., Kettlun, C.S., Chiu, W., and Mignery, G.A. (2003). Structure of the type 1
