scholarly journals Chemoreceptors in Caulobacter crescentus: Trimers of Receptor Dimers in a Partially Ordered Hexagonally Packed Array

2008 ◽  
Vol 190 (20) ◽  
pp. 6805-6810 ◽  
Author(s):  
Cezar M. Khursigara ◽  
Xiongwu Wu ◽  
Sriram Subramaniam
Keyword(s):  
Caulobacter Crescentus ◽  
Electron Tomography ◽  
Bacterial Chemotaxis ◽  
Bacterial Cells ◽  
Molecular Architecture ◽  
Cellular Motility ◽  
Partially Ordered ◽  
Order And Disorder ◽  
Cryo Electron Tomography ◽  
Receptor Dimers

ABSTRACT Chemoreceptor arrays are macromolecular complexes that form extended assemblies primarily at the poles of bacterial cells and mediate chemotaxis signal transduction, ultimately controlling cellular motility. We have used cryo-electron tomography to determine the spatial distribution and molecular architecture of signaling molecules that comprise chemoreceptor arrays in wild-type Caulobacter crescentus cells. We demonstrate that chemoreceptors are organized as trimers of receptor dimers, forming partially ordered hexagonally packed arrays of signaling complexes in the cytoplasmic membrane. This novel organization at the threshold between order and disorder suggests how chemoreceptors and associated molecules are arranged in signaling assemblies to respond dynamically in the activation and adaptation steps of bacterial chemotaxis.

scholarly journals An Economical, Portable Manual Cryogenic Plunge Freezer for the Preparation of Vitrified Biological Samples for Cryogenic Electron Microscopy

2020 ◽  
Vol 26 (3) ◽  
pp. 413-418
Author(s):  
Jamie S. Depelteau ◽  
Gert Koning ◽  
Wen Yang ◽  
Ariane Briegel
Keyword(s):  
Electron Microscopy ◽  
Electron Tomography ◽  
Particle Analysis ◽  
Bacterial Cells ◽  
Cellular Processes ◽  
Cryo Electron Tomography ◽  
Specialized Equipment ◽  
Improved Design ◽  
Commercial Equipment ◽  
Local Machine

AbstractVisualizing biological structures and cellular processes in their native state is a major goal of many scientific laboratories. In the past 20 years, the technique of preserving samples by vitrification has greatly expanded, specifically for use in cryogenic electron microscopy (cryo-EM). Here, we report on improvements in the design and use of a portable manual cryogenic plunge freezer that is intended for use in laboratories that are not equipped for the cryopreservation of samples. The construction of the instrument is economical, can be produced by a local machine shop without specialized equipment, and lowers the entry barriers for newcomers with a reliable alternative to costly commercial equipment. The improved design allows for successful freezing of isolated proteins for single particle analysis as well as bacterial cells for cryo-electron tomography. With this instrument, groups will be able to prepare vitreous samples whenever and wherever necessary, which can then be imaged at local or national cryo-EM facilities.

scholarly journals Cryo-Electron Tomography and Computer Simulations Reveal Distinct CheA Kinase Conformation in Bacterial Chemotaxis Signaling Receptor Complex

2015 ◽  
Vol 108 (2) ◽  
pp. 418a
Author(s):  
Benjamin A. Himes ◽  
C. Keith Cassidy ◽  
Jun Ma ◽  
Frances Joan D. Alvarez ◽  
Juan R. Perilla ◽  
...  
Keyword(s):  
Computer Simulations ◽  
Electron Tomography ◽  
Bacterial Chemotaxis ◽  
Receptor Complex ◽  
Cryo Electron Tomography

scholarly journals Molecular architecture of inner dynein arms in situ in Chlamydomonas reinhardtii flagella

2008 ◽  
Vol 183 (5) ◽  
pp. 923-932 ◽  
Author(s):  
Khanh Huy Bui ◽  
Hitoshi Sakakibara ◽  
Tandis Movassagh ◽  
Kazuhiro Oiwa ◽  
Takashi Ishikawa
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Electron Tomography ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Molecular Architecture ◽  
Heavy Chains ◽  
Distal Side ◽  
Cryo Electron Tomography ◽  
Dynein Arms

The inner dynein arm regulates axonemal bending motion in eukaryotes. We used cryo-electron tomography to reconstruct the three-dimensional structure of inner dynein arms from Chlamydomonas reinhardtii. All the eight different heavy chains were identified in one 96-nm periodic repeat, as expected from previous biochemical studies. Based on mutants, we identified the positions of the AAA rings and the N-terminal tails of all the eight heavy chains. The dynein f dimer is located close to the surface of the A-microtubule, whereas the other six heavy chain rings are roughly colinear at a larger distance to form three dyads. Each dyad consists of two heavy chains and has a corresponding radial spoke or a similar feature. In each of the six heavy chains (dynein a, b, c, d, e, and g), the N-terminal tail extends from the distal side of the ring. To interact with the B-microtubule through stalks, the inner-arm dyneins must have either different handedness or, more probably, the opposite orientation of the AAA rings compared with the outer-arm dyneins.

Dissecting the molecular architecture of integrin adhesion sites by cryo-electron tomography

2010 ◽  
Vol 12 (9) ◽  
pp. 909-915 ◽  
Author(s):  
Israel Patla ◽  
Tova Volberg ◽  
Nadav Elad ◽  
Vera Hirschfeld-Warneken ◽  
Carsten Grashoff ◽  
...  
Keyword(s):  
Electron Tomography ◽  
Molecular Architecture ◽  
Adhesion Sites ◽  
Cryo Electron Tomography

scholarly journals The molecular architecture of engulfment during Bacillus subtilis sporulation

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Kanika Khanna ◽  
Javier Lopez-Garrido ◽  
Ziyi Zhao ◽  
Reika Watanabe ◽  
Yuan Yuan ◽  
...  
Keyword(s):  
Bacillus Subtilis ◽  
Mother Cell ◽  
Cell Biology ◽  
Focused Ion Beam ◽  
High Spatial Resolution ◽  
Electron Tomography ◽  
Ion Beam ◽  
Molecular Architecture ◽  
Native State ◽  
Cryo Electron Tomography

The study of bacterial cell biology is limited by difficulties in visualizing cellular structures at high spatial resolution within their native milieu. Here, we visualize Bacillus subtilis sporulation using cryo-electron tomography coupled with cryo-focused ion beam milling, allowing the reconstruction of native-state cellular sections at molecular resolution. During sporulation, an asymmetrically-positioned septum generates a larger mother cell and a smaller forespore. Subsequently, the mother cell engulfs the forespore. We show that the septal peptidoglycan is not completely degraded at the onset of engulfment. Instead, the septum is uniformly and only slightly thinned as it curves towards the mother cell. Then, the mother cell membrane migrates around the forespore in tiny finger-like projections, whose formation requires the mother cell SpoIIDMP protein complex. We propose that a limited number of SpoIIDMP complexes tether to and degrade the peptidoglycan ahead of the engulfing membrane, generating an irregular membrane front.

scholarly journals Three-Dimensional Electron Microscopic Imaging of Membrane Invaginations in Escherichia coli Overproducing the Chemotaxis Receptor Tsr

2004 ◽  
Vol 186 (15) ◽  
pp. 5052-5061 ◽  
Author(s):  
Jonathan Lefman ◽  
Peijun Zhang ◽  
Teruhisa Hirai ◽  
Robert M. Weis ◽  
Jemma Juliani ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Electron Tomography ◽  
Three Dimensional ◽  
Bacterial Chemotaxis ◽  
Molecular Architecture ◽  
Electron Microscopic ◽  
E Coli ◽  
Macromolecular Assemblies ◽  
Membrane Networks ◽  
Receptor Clusters

ABSTRACT Electron tomography is a powerful method for determining the three-dimensional structures of large macromolecular assemblies, such as cells, organelles, and multiprotein complexes, when crystallographic averaging methods are not applicable. Here we used electron tomographic imaging to determine the molecular architecture of Escherichia coli cells engineered to overproduce the bacterial chemotaxis receptor Tsr. Tomograms constructed from fixed, cryosectioned cells revealed that overproduction of Tsr led to formation of an extended internal membrane network composed of stacks and extended tubular structures. We present an interpretation of the tomogram in terms of the packing arrangement of Tsr using constraints derived from previous X-ray and electron-crystallographic studies of receptor clusters. Our results imply that the interaction between the cytoplasmic ends of Tsr is likely to stabilize the presence of the membrane networks in cells overproducing Tsr. We propose that membrane invaginations that are potentially capable of supporting axial interactions between receptor clusters in apposing membranes could also be present in wild-type E. coli and that such receptor aggregates could play an important role in signal transduction during bacterial chemotaxis.

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