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Related Concept Videos

Formation of Higher-order Actin Filaments01:11

Formation of Higher-order Actin Filaments

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The polymerization of G-actin monomers into filamentous F-actin is a multi-step process. Once the F-actins are formed, they can bundle together in different arrangements to form higher-order networks and regulate cellular functions. Common examples include the formation of lamellipodia and filopodia at the cell's leading edge by actin reorganization in a migrating cell. The microvilli on the brush border epithelial cells are also formed through the F-actin network.
The high-order actin...
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Generation of Straight or Branched Actin Filaments01:14

Generation of Straight or Branched Actin Filaments

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The straight or branched structure formation of actin filaments is controlled by nucleating proteins such as the formins and Arp2/3 complex. Formin-mediated assembly results in straight filaments, whereas Arp2/3 protein complex-mediated assembly results in branched actin filaments.
Arp2/3 Complex
Arp2/3 complex is a seven-subunit complex consisting of two proteins similar to actin- Arp2 and Arp3, and five other subunits that help keep Arp2 and Arp3 inactive. When required, the complex is...
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Actin Polymerization01:42

Actin Polymerization

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Actin polymerization occurs through the head-to-tail association of binding sites on monomeric actin or G-actin to form filamentous or F-actin. The polymerization can be divided into three phases ̶  nucleation, elongation, and steady-state phase.
The nucleation phase involves forming a stable nucleus consisting of three actin monomers to form a new actin filament. Actin-binding proteins such as formins and Arp2/3 complex help filament growth post-nucleation. The Formins form straight...
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Introduction to Actin01:26

Introduction to Actin

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Actin is a highly conserved cytoskeletal protein found abundantly in eukaryotic cells. It constitutes 10% weight of the total cellular protein in muscle cells, while in non-muscle cells, it is lower and makes up around 1–5 percent of the total cell protein. Actin found in the unicellular amoebae and complex multicellular animals is around 80% similar, demonstrating their conservation over a billion years of evolution.  Actin coding genes are conserved within species and across...
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Assembly of Cytoskeletal Filaments01:18

Assembly of Cytoskeletal Filaments

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Cytoskeletal filaments are polymeric forms of smaller protein subunits. However, individual cytoskeletal filaments may easily disassemble or associate with other similar filaments to form rigid structures. Microfilaments, made of actin monomers, rely on actin-binding proteins to form bundles and create networks of individual actin filaments. Microtubules rely on microtubule-associated proteins (MAPs) to form sturdy cylindrical structures. However, the proteins involved in forming complex...
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The Structure of Intermediate Filaments01:19

The Structure of Intermediate Filaments

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The intermediate filaments are one of three widely studied cytoskeletal filaments. They are so named as their diameter (10 nm) is in between that of microfilaments (7 nm) and the microtubules (25 nm).  These filaments are highly stable and can remain intact when exposed to high salt concentrations and detergents. These filaments are responsible for providing stability and mechanical support to the cells. They also help in cell adhesion and maintaining tissue integrity.
Intermediate...
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Updated: May 28, 2025

A Graphical User Interface for Software-assisted Tracking of Protein Concentration in Dynamic Cellular Protrusions
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Structure of the F-tractin-F-actin complex.

Dmitry Shatskiy1, Athul Sivan2, Roland Wedlich-Söldner2

  • 1Membrane Enzymology Group, Groningen Institute of Biomolecular Sciences and Biotechnology (GBB), Faculty of Science and Engineering, University of Groningen , Groningen, The Netherlands.

The Journal of Cell Biology
|February 10, 2025
PubMed
Summary
This summary is machine-generated.

F-tractin peptide imaging actin cytoskeleton can impair cell migration. Researchers optimized F-tractin by removing a region, reducing bundling while maintaining actin labeling, and found it interacts similarly to Lifeact.

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In Vitro Polymerization of F-actin on Early Endosomes
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In Vitro Polymerization of F-actin on Early Endosomes
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Area of Science:

  • Cell Biology
  • Biochemistry
  • Structural Biology

Background:

  • F-tractin is a peptide probe for visualizing the actin cytoskeleton in live eukaryotic cells.
  • High expression levels of F-tractin have been linked to impaired cell migration and actin bundling.

Purpose of the Study:

  • To elucidate the structural basis for F-tractin's effects on cell migration and actin bundling.
  • To develop an optimized F-tractin variant with improved properties for actin visualization.

Main Methods:

  • Determined the cryo-electron microscopy (cryo-EM) structure of the F-tractin-F-actin complex.
  • Analyzed the structural contributions of F-tractin's N-terminal and C-terminal regions to actin binding and bundling.
  • Developed and characterized an optimized F-tractin based on structural insights.

Main Results:

  • The cryo-EM structure revealed F-tractin comprises a flexible N-terminal region and an amphipathic C-terminal helix.
  • The N-terminal region is dispensable for F-actin binding but responsible for actin bundling.
  • An optimized F-tractin lacking the N-terminal region showed minimized bundling and retained strong actin labeling.
  • The C-terminal helix interacts with a hydrophobic pocket on F-actin, a shared interaction site with Lifeact.

Conclusions:

  • F-tractin and Lifeact share analogous modes of interaction with F-actin.
  • The N-terminal region of F-tractin is key to its bundling effect.
  • The optimized F-tractin offers improved performance for actin cytoskeleton imaging.
  • This study provides structural insights for the development of novel actin probes.