Related Experiment Video
Updated: Jul 5, 2026
08:40
Reconstitution of Actin-Based Motility with Commercially Available Proteins
Published on: October 28, 2022
Actin nucleation: putting the brakes on Arp2/3
Britta Qualmann1, Michael M Kessels1
1Institute for Biochemistry I, Friedrich-Schiller-University Jena, 07743 Jena, Germany.
Current Biology : CB
|May 22, 2008
Summary
The Arp2/3 complex, an actin filament nucleator, has a newly discovered brake mechanism. This brake inhibits both its spontaneous and promoted activity, revealing a dual control system for actin dynamics.
Area of Science:
- Cell Biology
- Biochemistry
- Molecular Biology
Background:
- The Arp2/3 complex is a key regulator of actin cytoskeleton dynamics.
- It functions as a potent nucleator of branched actin filaments upon activation.
Purpose of the Study:
- To investigate the regulatory mechanisms controlling Arp2/3 complex activity.
- To identify factors that modulate both basal and activated states of the Arp2/3 complex.
Main Methods:
- Biochemical assays to measure Arp2/3 complex nucleation activity.
- In vitro reconstitution experiments with purified proteins.
- Analysis of protein-protein interactions.
Main Results:
- A novel inhibitory mechanism, or 'brake,' acting on the Arp2/3 complex was identified.
- This brake suppresses the intrinsic basal activity of the Arp2/3 complex.
- The brake also inhibits Arp2/3 complex activation by nucleation-promoting factors.
Conclusions:
- Arp2/3 complex activity is regulated by both positive and negative control mechanisms.
- The newly discovered brake provides a crucial counterbalance to Arp2/3 complex activation.
- Understanding this dual regulation is essential for comprehending actin dynamics in cellular processes.
Related Concept Videos
01:14Generation 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...
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...
01:42Actin 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...
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...
01:31Mechanism of Lamellipodia Formation
Cells migrating in response to external stimuli form lamellipodia, which are thin membrane protrusions supported by a mesh of linked, branched, or unbranched actin filaments. These actin filaments interact with myosin motor proteins, creating the dynamic actomyosin complex within the cytoskeleton. Contractility, or the ability to generate contractile stress, is inherent to the actomyosin complex. It helps cells detect the stiffness of the surrounding ECM and exert contractile force for...
01:11Formation 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...
The high-order actin networks...
02:37Restarting Stalled Replication Forks
DNA replication is initiated at sites containing predefined DNA sequences known as origins of replication. DNA is unwound at these sites by the minichromosome maintenance (MCM) helicase and other factors such as Cdc45 and the associated GINS complex.The unwound single strands are protected by replication protein A (RPA) until DNA polymerase starts synthesizing DNA at the 5’ end of the strand in the same direction as the replication fork. To prevent the replication fork from falling apart, a...
01:19Actin 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...
In F-actin, the ADF/cofilin proteins...