Faculty Opinions recommendation of Cryo-electron tomography structure of Arp2/3 complex in cells reveals new insights into the branch junction.

AbstractThe actin-related protein (Arp)2/3 complex nucleates branched actin filament networks pivotal for cell migration, endocytosis and pathogen infection. Its activation is tightly regulated and involves complex structural rearrangements and actin filament binding, which are yet to be understood. Here, we report a 9.0 Å resolution structure of the actin filament Arp2/3 complex branch junction in cells using cryo-electron tomography and subtomogram averaging. This allows us to generate an accurate model of the active Arp2/3 complex in the branch junction and its interaction with actin filaments. Notably, our model reveals a previously undescribed set of interactions of the Arp2/3 complex with the mother filament, significantly different to the previous branch junction model. Our structure also indicates a central role for the ArpC3 subunit in stabilizing the active conformation.

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Novel cryo-electron tomography structure of Arp2/3 complex in cells reveals mechanisms of branch formation

10.1101/2020.08.25.266262 ◽

2020 ◽

Author(s):

Florian Fäßler ◽

Georgi Dimchev ◽

Victor-Valentin Hodirnau ◽

William Wan ◽

Florian KM Schur

Keyword(s):

Actin Filament ◽

Electron Tomography ◽

Cryo Electron Tomography ◽

Branch Formation ◽

Complex Structural ◽

Filament Networks ◽

Subtomogram Averaging ◽

Resolution Structure ◽

In Cells

AbstractThe actin-related protein (Arp)2/3 complex nucleates branched actin filament networks pivotal for cell migration, endocytosis and pathogen infection. Its activation is tightly regulated and involves complex structural rearrangements and actin filament binding, which are yet to be understood. Here, we report a 9.0Å resolution structure of the actin filament Arp2/3 complex branch junction in cells using cryo-electron tomography and subtomogram averaging. This allows us to generate an accurate model of the active Arp2/3 complex in the branch junction and its interaction with actin filaments. Our structure indicates a central role for the ArpC3 subunit in stabilizing the active conformation and suggests that in the branch junction relocation of the ArpC5 N-terminus and the C-terminal tail of Arp3 is important to fix Arp2 and Arp3 in an actin dimer-like conformation. Notably, our model of the branch junction in cells significantly differs from the previous in vitro branch junction model.

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1S-B2-2In Situ Structural Studies of Macro Molecular Complexes in Cells by Cryo-electron Tomography with Volta Phase Plate

Microscopy ◽

10.1093/jmicro/dfx047 ◽

2017 ◽

Vol 66 (suppl_1) ◽

pp. i9-i9

Author(s):

Yoshiyuki Fukuda ◽

Florian Beck ◽

Wolfgang Baumeister

Keyword(s):

Electron Tomography ◽

Molecular Complexes ◽

Phase Plate ◽

Structural Studies ◽

Cryo Electron Tomography ◽

In Cells

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Microtubule architecture in vitro and in cells revealed by cryo-electron tomography

Acta Crystallographica Section D Structural Biology ◽

10.1107/s2059798318001948 ◽

2018 ◽

Vol 74 (6) ◽

pp. 572-584 ◽

Cited By ~ 29

Author(s):

Joseph Atherton ◽

Melissa Stouffer ◽

Fiona Francis ◽

Carolyn A. Moores

Keyword(s):

Molecular Motors ◽

Electron Tomography ◽

Three Dimensional ◽

Structural Heterogeneity ◽

Dimensional Structure ◽

Cellular Functions ◽

Cellular Processes ◽

Cryo Electron Tomography ◽

In Cells

The microtubule cytoskeleton is involved in many vital cellular processes. Microtubules act as tracks for molecular motors, and their polymerization and depolymerization can be harnessed to generate force. The structures of microtubules provide key information about the mechanisms by which their cellular roles are accomplished and the physiological context in which these roles are performed. Cryo-electron microscopy allows the visualization of in vitro-polymerized microtubules and has provided important insights into their overall morphology and the influence of a range of factors on their structure and dynamics. Cryo-electron tomography can be used to determine the unique three-dimensional structure of individual microtubules and their ends. Here, a previous cryo-electron tomography study of in vitro-polymerized GMPCPP-stabilized microtubules is revisited, the findings are compared with new tomograms of dynamic in vitro and cellular microtubules, and the information that can be extracted from such data is highlighted. The analysis shows the surprising structural heterogeneity of in vitro-polymerized microtubules. Lattice defects can be observed both in vitro and in cells. The shared ultrastructural properties in these different populations emphasize the relevance of three-dimensional structures of in vitro microtubules for understanding microtubule cellular functions.

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