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Related Concept Videos

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 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.
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...
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...
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...
Assembly of Cytoskeletal Filaments01:18

Assembly of Cytoskeletal Filaments

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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Related Experiment Video

Updated: Jun 4, 2026

Reconstitution of Actin-Based Motility with Commercially Available Proteins
08:40

Reconstitution of Actin-Based Motility with Commercially Available Proteins

Published on: October 28, 2022

Actin structure and function.

Roberto Dominguez1, Kenneth C Holmes

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

Annual Review of Biophysics
|February 15, 2011
PubMed
Summary
This summary is machine-generated.

Actin, a vital protein in eukaryotic cells, forms filaments essential for cell structure, motility, and muscle contraction. Its dynamic polymerization is regulated by various factors and proteins, crucial for cellular functions.

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Measuring Protein Binding to F-actin by Co-sedimentation
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Measuring Protein Binding to F-actin by Co-sedimentation

Published on: May 18, 2017

Area of Science:

  • Cell Biology
  • Biochemistry
  • Structural Biology

Background:

  • Actin is the most abundant protein in eukaryotic cells, involved in numerous protein-protein interactions.
  • It plays critical roles in cellular functions including motility, shape maintenance, polarity, and transcription regulation.
  • The actin cytoskeleton is a target for various pathogens.

Purpose of the Study:

  • To review the structures of monomeric (G-actin) and filamentous (F-actin).
  • To discuss the interactions governing actin polymerization and disassembly.

Main Methods:

  • Review of existing structural data for G-actin and F-actin.
  • Analysis of literature on actin-binding proteins and regulatory mechanisms.

Main Results:

  • Detailed structural insights into G-actin and F-actin states.
  • Identification of key interactions controlling actin dynamics.

Conclusions:

  • Actin's structural versatility and dynamic polymerization are fundamental to its diverse cellular roles.
  • Understanding actin structure and regulation is crucial for comprehending cellular processes and disease mechanisms.