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Related Concept Videos

Actin Filament Depolymerization01:19

Actin Filament Depolymerization

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Actin filaments (F-actin) are composed of actin subunits. The dissociation of actin monomers can occur from either end of F-actin. The rate of dissociation is faster from the minus-end or the pointed end, where the actin subunits exist with a bound ADP, together known as ADP-actin. The depolymerization of F-actin is aided by proteins, including the actin-depolymerizing factor (ADF) and cofilin family of proteins, gelsolin, and glia maturation factor (GMF).
In F-actin, the ADF/cofilin proteins...
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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 Treadmilling01:18

Actin Treadmilling

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Actin filaments undergo polymerization and depolymerization from either end. The polymerization and depolymerization rates depend on the cytosolic concentration of free G-actins. The polymerization rate is generally higher at the plus or barbed end, while the depolymerization rate is higher at the minus or pointed end. At a steady state, critical concentration describes the concentration of free G-actin monomers at which the polymerization rate at the plus end is equal to that of the...
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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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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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Related Experiment Video

Updated: Feb 4, 2026

Quantification of Filamentous Actin F-actin Puncta in Rat Cortical Neurons
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Quantification of Filamentous Actin F-actin Puncta in Rat Cortical Neurons

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Latrunculin A Accelerates Actin Filament Depolymerization in Addition to Sequestering Actin Monomers.

Ikuko Fujiwara1, Mark E Zweifel2, Naomi Courtemanche2

  • 1Frontier Research Institute for Materials Science, Nagoya Institute of Technology, Gokiso, Showa-ku, Nagoya 466-8555, Japan; Department of Molecular Cellular and Developmental Biology, Yale University, PO Box 208103, New Haven, CT 06520, USA.

Current Biology : CB
|October 2, 2018
PubMed
Summary

Latrunculin A (LatA) rapidly depolymerizes actin filaments by binding monomers and promoting phosphate release from filament ends. This mechanism, distinct from simple monomer sequestration, also involves filament severing.

Keywords:
ADPATPactincapping proteindepolymerizationforminlatrunculin Aphosphatepolymerization

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Using Microfluidics and Fluorescence Microscopy to Study the Assembly Dynamics of Single Actin Filaments and Bundles
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Using Microfluidics and Fluorescence Microscopy to Study the Assembly Dynamics of Single Actin Filaments and Bundles

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Actin Co-Sedimentation Assay; for the Analysis of Protein Binding to F-Actin
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Actin Co-Sedimentation Assay; for the Analysis of Protein Binding to F-Actin

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Related Experiment Videos

Last Updated: Feb 4, 2026

Quantification of Filamentous Actin F-actin Puncta in Rat Cortical Neurons
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Quantification of Filamentous Actin F-actin Puncta in Rat Cortical Neurons

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Using Microfluidics and Fluorescence Microscopy to Study the Assembly Dynamics of Single Actin Filaments and Bundles
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Actin Co-Sedimentation Assay; for the Analysis of Protein Binding to F-Actin
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Actin Co-Sedimentation Assay; for the Analysis of Protein Binding to F-Actin

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Area of Science:

  • Cell Biology
  • Biochemistry
  • Biophysics

Background:

  • Latrunculin A (LatA) is a key reagent for depolymerizing actin filaments in live cells.
  • Its mechanism is primarily attributed to sequestering actin monomers, preventing polymerization.

Purpose of the Study:

  • To investigate the detailed mechanism of LatA-induced actin depolymerization.
  • To determine the binding affinities of LatA to different actin monomer states and actin filaments.

Main Methods:

  • Total Internal Reflection Fluorescence (TIRF) microscopy of single muscle actin filaments.
  • Measurement of LatA binding affinities (Kd) to ATP-actin, ADP-Pi-actin, and ADP-actin monomers.
  • Analysis of filament depolymerization rates and severing activity at varying LatA concentrations.

Main Results:

  • LatA exhibits higher affinity for ATP-actin monomers (Kd = 0.1 μM) than ADP-actin (Kd = 4.7 μM).
  • LatA slowly severs filaments and increases depolymerization rates of ATP-actin filaments, but not ADP-actin filaments.
  • LatA binds weakly to actin filaments (Kd > 100 μM), suggesting a distinct interaction with polymerized actin.

Conclusions:

  • LatA's effect on actin filaments involves more than just monomer sequestration.
  • LatA promotes phosphate dissociation from filament ends, leading to depolymerization limited by ADP-actin dissociation.
  • Cellular effects of LatA should consider both monomer binding, filament severing, and end-directed depolymerization.