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Related Concept Videos

Generation of Straight or Branched Actin Filaments01:14

Generation of Straight or Branched Actin Filaments

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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...
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Actin Polymerization01:42

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

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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...
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Mechanism of Lamellipodia Formation01:31

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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...
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Mechanism of Filopodia Formation01:39

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Filopodia are thin, actin-rich cellular protrusions that play an important role in many fundamental cellular functions. They vary in their occurrence, length, and positioning in different cell types, suggesting their diverse roles.
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Introduction to Actin01:26

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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...
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Updated: Apr 2, 2026

Reconstitution of Actin-Based Motility with Commercially Available Proteins
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Bacterial nucleators: actin' on actin.

Joana N Bugalhão1, Luís Jaime Mota1, Irina S Franco2

  • 1UCIBIO-REQUIMTE, Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal.

Pathogens and Disease
|September 30, 2015
PubMed
Summary
This summary is machine-generated.

Bacteria use unique actin nucleator proteins to manipulate host cells during infection. These bacterial effectors mimic eukaryotic actin assembly factors, revealing new insights into host-pathogen interactions and cellular processes.

Keywords:
actinbacterial virulenceeffector proteinnucleationsecretion system

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Area of Science:

  • Microbiology
  • Cell Biology
  • Biochemistry

Background:

  • Microbial pathogens target the actin cytoskeleton to facilitate infection.
  • Bacterial effector proteins often disrupt actin dynamics by targeting the Arp2/3 complex.
  • A novel class of bacterial effectors directly nucleates actin, mimicking eukaryotic assembly factors.

Purpose of the Study:

  • To review a recently identified class of bacterial actin nucleator proteins.
  • To explore how these effectors mimic eukaryotic actin assembly pathways.
  • To understand the broader cellular consequences of bacterial actin manipulation.

Main Methods:

  • Focus on structural and functional analyses of bacterial actin nucleators.
  • Comparison of bacterial nucleators with eukaryotic actin assembly factors (formin, WH2, Ena/VASP).
  • Investigation of effects beyond actin polymerization, including host cell functions.

Main Results:

  • Gram-negative bacteria employ direct actin nucleators that mimic eukaryotic assembly factors.
  • These bacterial proteins utilize shared motifs and mechanisms with eukaryotic nucleators.
  • Bacterial actin manipulation impacts host vesicle trafficking, cell cycle, and cell death.

Conclusions:

  • Bacteria have evolved effectors to co-opt diverse eukaryotic actin assembly pathways.
  • Bacterial actin nucleators offer insights into fundamental actin polymerization mechanisms.
  • Studying these effectors can illuminate connections between actin dynamics and other cellular processes.