Lecture Notes: Microtubules and Intermediate Filaments

Introduction

• Online classes are conducted by various teachers.
• Test series includes 30,000+ practice questions with video solutions.
• Microfilaments: Made of actins, dependent on ATP.

Microtubules

• Composed of alpha and beta tubulin proteins.
• Bind to GTP.
• Dynamic for polymerization and depolymerization.
• Polarized, with positive and negative ends.

Microtubule Structure

• 13 protofilaments come together to form a microtubule.
• Present as singlet, doublet, and triplet.

Microtubule Organizing Center (MTOC)

• Plays a crucial role in the nucleation of microtubules.
• Centrosome is the primary MTOC in animal cells.

Dynamic Instability

• Rapid interconversion between growth and shrinking.
• Catastrophe promotes disassembly, while rescue promotes assembly.

Proteins and Drugs

• Stathmin and Kinesin 13 promote catastrophe.
• Katanin promotes microtubule breakage.
• Taxol inhibits depolymerization.
• Nocodazole and Colchicine promote depolymerization.

Intermediate Filaments

• Primary building block: Dimer, forming staggered tetramer.
• Five types: Keratins, Desmin, GFAP, Vimentin, Neurofilaments, and Lamin.

Characteristics

• Different cells have different types of filaments.
• Rich in cysteine and form disulfide bridges.

Lamins and Laminopathies

• Help maintain the integrity of the nuclear envelope.
• Cause diseases like progeria.

Other Notes

• Septins: GTP-binding proteins that form non-polar filaments.

Conclusion

• Microtubules and intermediate filaments play a crucial role in cell structure and function.
• Various proteins and drugs affect their assembly and disassembly.