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Related Concept Videos

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...
Generation of Straight or Branched Actin Filaments01:14

Generation of Straight or Branched Actin Filaments

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...
Formation of Higher-order Actin Filaments01:11

Formation of Higher-order Actin Filaments

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 networks...
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.
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...
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.

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Related Experiment Video

Updated: Jun 16, 2026

Tuning the Contractility and Deformation Modes of Active Actin-Based Assemblies In Vitro: From Two-Dimensional Active Networks to Liquid Crystal Drops
06:48

Tuning the Contractility and Deformation Modes of Active Actin-Based Assemblies In Vitro: From Two-Dimensional Active Networks to Liquid Crystal Drops

Published on: July 11, 2025

Structural insights into de novo actin polymerization.

Roberto Dominguez1

  • 1Department of Physiology, 3700 Hamilton Walk, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6085, USA. droberto@mail.med.upenn.edu

Current Opinion in Structural Biology
|January 26, 2010
PubMed
Summary

Cellular actin polymerization is complex, requiring specific factors to overcome kinetic barriers. These factors, including W domains and profilin-actin binding, are crucial for actin cytoskeleton remodeling and cell function.

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Reconstitution of Actin-Based Motility with Commercially Available Proteins
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Reconstitution of Actin-Based Motility with Commercially Available Proteins

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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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Tuning the Contractility and Deformation Modes of Active Actin-Based Assemblies In Vitro: From Two-Dimensional Active Networks to Liquid Crystal Drops
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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

Published on: May 5, 2022

Area of Science:

  • Cellular biology
  • Biochemistry
  • Structural biology

Background:

  • Actin polymerization/depolymerization is vital for cellular functions.
  • De novo actin polymerization is kinetically challenging due to unstable intermediates and monomer binding proteins.
  • Cells utilize filament nucleation and elongation factors to regulate actin dynamics.

Purpose of the Study:

  • To elucidate the mechanisms of actin filament nucleation and elongation factors.
  • To understand how these factors initiate, regulate, and mediate actin polymerization.
  • To explore the structural roles of domains like W domains and proline-rich regions.

Main Methods:

  • Structural biology techniques to analyze protein structures and interactions.
  • Biochemical assays to study actin binding and polymerization kinetics.
  • Investigating the role of specific protein domains (W domain, Pro-rich regions) and their interactions.

Main Results:

  • Identified diverse mechanisms employed by nucleation and elongation factors.
  • Highlighted the role of W domain tandem repeats in recruiting actin subunits.
  • Demonstrated the importance of Pro-rich regions in binding profilin-actin complexes.
  • Showcased the interaction between these factors and Rho-family GTPases.

Conclusions:

  • Actin nucleation and elongation factors are essential regulators of the actin cytoskeleton.
  • Specific protein domains and their arrangements dictate actin recruitment and polymerization.
  • Profilin-actin complexes are a key source of polymerizable actin.
  • Regulation of actin dynamics is tightly linked to signaling pathways involving Rho GTPases.