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Related Concept Videos

Actin Filament Depolymerization01:19

Actin Filament Depolymerization

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...
Toxoplasmosis01:28

Toxoplasmosis

Toxoplasmosis, a zoonotic disease caused by the protozoan Toxoplasma gondii, poses significant public health challenges globally due to its high seroprevalence and varied clinical manifestations. As an obligate intracellular parasite, T. gondii can infect all warm-blooded vertebrates, but felids are its only definitive hosts, shedding unsporulated oocysts into the environment. Humans typically acquire the infection through ingestion of tissue cysts in undercooked meat or oocysts from...
Actin Polymerization01:42

Actin Polymerization

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 actin...
Actin Treadmilling01:18

Actin Treadmilling

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...
Actin Polymerization and Cell Motility01:13

Actin Polymerization and Cell Motility

Actin is a family of globular proteins that are highly abundant in eukaryotic cells. It makes up approximately 1-5% of total cell protein concentration. Actin monomers polymerize to form a complex network of polarized filaments, the actin cytoskeleton, that plays a crucial role in many cellular processes, including cell motility, division, endocytosis, and metastasis of cancer cells.
Actin cytoskeleton dynamics can produce pushing, pulling, and resistance forces that help the cell to migrate.
Introduction to Actin01:26

Introduction to Actin

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 different species.

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Related Experiment Video

Updated: Jun 17, 2026

Genetic Manipulation in &Delta;ku80 Strains for Functional Genomic Analysis of Toxoplasma gondii
09:52

Genetic Manipulation in Δku80 Strains for Functional Genomic Analysis of Toxoplasma gondii

Published on: July 12, 2013

Toxoplasma gondii actin depolymerizing factor acts primarily to sequester G-actin.

Simren Mehta1, L David Sibley

  • 1Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.

The Journal of Biological Chemistry
|January 1, 2010
PubMed
Summary
This summary is machine-generated.

Toxoplasma gondii actin depolymerizing factor (ADF) promotes rapid actin filament turnover by weakening filament severing and strongly sequestering monomers. This dual action maintains high G-actin levels, crucial for parasite motility.

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Forward Genetics Screens Using Macrophages to Identify Toxoplasma gondii Genes Important for Resistance to IFN-&#947;-Dependent Cell Autonomous Immunity
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Area of Science:

  • Parasitology
  • Cell Biology
  • Biochemistry

Background:

  • Toxoplasma gondii, an apicomplexan parasite, relies on actin filaments for gliding motility.
  • High G-actin concentrations suggest rapid actin filament turnover, but disassembly mechanisms are unclear.
  • Actin depolymerizing factor (ADF)/cofilin proteins regulate actin turnover in eukaryotes.

Purpose of the Study:

  • To investigate the mechanism of actin filament turnover regulation by T. gondii ADF (TgADF).
  • To understand how TgADF interacts with T. gondii actin (TgACT) and influences filament dynamics.

Main Methods:

  • Biochemical assays to analyze TgADF's severing and monomer-sequestering activities.
  • Investigated TgADF interaction with T. gondii actin (TgACT) oligomers and filaments.
  • Compared TgADF activity with and without key F-actin binding sites.

Main Results:

  • TgADF exhibits weak filament severing activity compared to other ADF/cofilin proteins.
  • TgADF strongly sequesters G-actin monomers, inhibiting polymerization at low concentrations.
  • Restoring F-actin binding sites reduced TgADF's net filament disassembly activity.

Conclusions:

  • TgADF facilitates rapid actin filament turnover through a dual mechanism: weak severing and strong monomer sequestration.
  • This process maintains high G-actin concentrations, essential for T. gondii motility.
  • TgADF's unique properties highlight novel actin regulation strategies in Apicomplexa.