Related Experiment Video
Updated: Jun 20, 2026
06:54
A Time-Efficient Fluorescence Spectroscopy-Based Assay for Evaluating Actin Polymerization Status in Rodent and Human Brain Tissues
Published on: June 3, 2021
Structural plasticity in actin and tubulin polymer dynamics.
Hao Yuan Kueh1, Timothy J Mitchison
1Department of Systems Biology, Harvard Medical School, Boston, MA 02215, USA.
Science (New York, N.Y.)
|August 22, 2009
Summary
Actin filaments and microtubules exhibit structural plasticity, challenging the traditional view that nucleotide state solely dictates polymerization dynamics. This plasticity influences polymer behavior and cellular functions.
Area of Science:
- Cell Biology
- Biophysics
- Biochemistry
Background:
- Actin filaments and microtubules are crucial cytoskeletal polymers involved in cell organization, division, and motility.
- The established treadmilling theory posits that bound nucleotide states (ATP for actin, GTP for tubulin) govern polymerization and depolymerization rates.
- Existing observations suggest polymer dynamics are influenced by structural states beyond the bound nucleotide.
Purpose of the Study:
- To challenge the conventional chemical kinetics model of cytoskeletal polymer dynamics.
- To introduce and discuss the concept of "structural plasticity" in actin filaments and microtubules.
- To highlight the role of structural plasticity in polymer dynamics and cellular functions.
Main Methods:
- Literature review and synthesis of existing experimental data.
- Theoretical discussion of polymer dynamics.
- Conceptual framework development.
Main Results:
- The traditional chemical kinetics model is insufficient to explain observed polymerization dynamics.
- Multiple structural states of polymers exist, independent of the bound nucleotide state.
- These structural states, termed "structural plasticity," significantly impact polymerization rates.
Conclusions:
- Structural plasticity is a key factor in the dynamic behavior of actin filaments and microtubules.
- Revisiting polymer dynamics through the lens of structural plasticity is essential for understanding cellular functions.
- Emerging evidence supports the central role of structural plasticity in cytoskeletal polymer function.
More Related Videos
09:10Reconstituting and Characterizing Actin-Microtubule Composites with Tunable Motor-Driven Dynamics and Mechanics
Published on: August 25, 2022
06:48Tuning 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
Related Concept Videos
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...
02:17Microtubule Instability
Microtubules are hollow cylindrical filaments having a diameter of approximately 25 nm and a length that varies from 200 nm to 25 μm. GTP-bound tubulin subunits form αβ-heterodimers for microtubule assembly. These core building blocks interact longitudinally, polymerizing into protofilaments. The protofilaments then interact with one another through lateral bonding forces to form stable cylindrical microtubules. These cylindrical filaments are dynamic as they undergo repeated assembly and...
01:18Actin 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...
01:13Actin 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.
Actin cytoskeleton dynamics can produce pushing, pulling, and resistance forces that help the cell to migrate.
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...
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...