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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.
The Role of Actin and Myosin in Non-muscle Cells01:10

The Role of Actin and Myosin in Non-muscle Cells

Actin and myosin or actomyosin filaments also play a significant role in cells other than those involved in muscle contraction (which occurs within the sarcomere of muscle cells). The mechanism of non-muscle cell contractile bundles was first observed in Dictyostelium and Acanthamoeba. In non-muscle cells, two bundles are commonly found: stress fibers and actomyosin adherence belts. These contractile bundles are smaller and less organized than the ones found in muscle cells. They  are held...
Actin and Myosin in Muscle Contraction01:16

Actin and Myosin in Muscle Contraction

Actin and myosin are contractile proteins that form the sarcomere found in skeletal muscle tissues for regulating muscle contraction. Actin, a globular contractile protein, interacts with myosin for muscle contraction. The skeletal tissue appears striped or striated under a microscope due to the repeated arrangement of contractile proteins actin and myosin along the length of myofibrils. Dark A bands and light I bands repeat along myofibrils, and the alignment of myofibrils in the cell causes...
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...

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Related Experiment Video

Updated: Jun 20, 2026

Analyzing the α-Actinin Network in Human iPSC-Derived Cardiomyocytes Using Single Molecule Localization Microscopy
07:02

Analyzing the α-Actinin Network in Human iPSC-Derived Cardiomyocytes Using Single Molecule Localization Microscopy

Published on: November 3, 2020

alpha-actinin-3 and performance.

Nan Yang, Fleur Garton, Kathryn North

    Medicine and Sport Science
    |August 22, 2009
    PubMed
    Summary
    This summary is machine-generated.

    The ACTN3 gene

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    Aip1p Dynamics Are Altered by the R256H Mutation in Actin
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    A Time-Efficient Fluorescence Spectroscopy-Based Assay for Evaluating Actin Polymerization Status in Rodent and Human Brain Tissues
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    A Time-Efficient Fluorescence Spectroscopy-Based Assay for Evaluating Actin Polymerization Status in Rodent and Human Brain Tissues

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    Related Experiment Videos

    Last Updated: Jun 20, 2026

    Analyzing the α-Actinin Network in Human iPSC-Derived Cardiomyocytes Using Single Molecule Localization Microscopy
    07:02

    Analyzing the α-Actinin Network in Human iPSC-Derived Cardiomyocytes Using Single Molecule Localization Microscopy

    Published on: November 3, 2020

    Aip1p Dynamics Are Altered by the R256H Mutation in Actin
    08:57

    Aip1p Dynamics Are Altered by the R256H Mutation in Actin

    Published on: July 30, 2014

    A Time-Efficient Fluorescence Spectroscopy-Based Assay for Evaluating Actin Polymerization Status in Rodent and Human Brain Tissues
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    A Time-Efficient Fluorescence Spectroscopy-Based Assay for Evaluating Actin Polymerization Status in Rodent and Human Brain Tissues

    Published on: June 3, 2021

    Area of Science:

    • Muscle physiology
    • Genetics
    • Sports science

    Background:

    • Human sarcomeric alpha-actinins (ACTN2 and ACTN3) are key Z-line proteins in skeletal muscle.
    • ACTN3 is specific to fast-twitch muscle fibers, crucial for high-velocity contractions.
    • A common ACTN3 R577X polymorphism leads to alpha-actinin-3 deficiency in some individuals.

    Purpose of the Study:

    • Investigate the functional impact of ACTN3 R577X genotype on muscle characteristics.
    • Determine the role of alpha-actinin-3 in athletic performance and muscle fiber adaptation.
    • Explore the evolutionary implications of the ACTN3 null-allele.

    Main Methods:

    • Analysis of ACTN3 R577X genotype frequencies in athletic populations.
    • Examination of muscle fiber characteristics in an Actn3 knockout mouse model.
    • Assessment of muscle strength, sprinting speed, and fiber-type specific adaptations.

    Main Results:

    • The ACTN3 XX genotype (null-allele homozygosity) is underrepresented in sprint athletes, indicating a detrimental effect on performance.
    • Actn3 knockout mice exhibit a shift from fast glycolytic to slow oxidative muscle fiber characteristics.
    • Alpha-actinin-3 deficiency is linked to decreased muscle mass, slower contraction, but increased fatigue resistance and oxidative capacity.

    Conclusions:

    • Loss of alpha-actinin-3 negatively impacts sprint performance by altering fast muscle fiber properties.
    • The shift towards oxidative metabolism in fast fibers may confer an evolutionary advantage.
    • The ACTN3 genotype contributes to natural variations in muscle performance and adaptation.