The cytoskeleton is like a support system for cells. It’s made up of a network of fibers that help the cell keep its shape, stay strong, and do its job. The cytoskeleton has three main parts: microfilaments, microtubules, and intermediate filaments. Special proteins help put these parts together and take them apart when needed.

Microfilaments

• Main Protein: Actin
  • What It Does: Actin helps form microfilaments, which are essential for helping the cell keep its shape and move around.
  • How It Works: Actin can be found in two forms:
    • Globular (G-actin)
    • Filamentous (F-actin)
  • To start making these filaments, there needs to be about $0.1\ \mu M$ of actin.

Microtubules

• Main Proteins: Tubulin (α-tubulin and β-tubulin)
  • What They Do: Tubulin proteins stick together to form microtubules. These microtubules help support the cell and act like roads for moving things inside the cell.
  • How They Work: Microtubules can grow quickly and shrink just as fast. They can grow at about $1.5\ \mu m/min$ and shrink up to $20\ \mu m/min$.

Intermediate Filaments

• Main Proteins: There are many types like keratins, vimentin, and neurofilaments.
  • What They Do: These help make cells strong and stable.
  • How They Work: Intermediate filaments are more stable than microfilaments and microtubules. How fast they get replaced depends on the type of cell, but it usually takes several days.

Regulatory Proteins

• Profilin and Cofilin (for actin): These proteins control how actin forms and breaks down.
• Stathmin (for tubulin): This protein stops microtubules from forming.
• Katanin (for microtubules): This one cuts microtubules, helping them break down.

Knowing about these proteins helps us understand how cells stay structured and adapt to their environments.