A microtubule is a hollow cylindrical structure built from 13 parallel protofilaments, each composed of αβ-tubulin heterodimers stacked head to tail and folded into a tube.

TLS Online TPP Program

#Id: 8334

#Unit 2. Cellular Organization

Phalloidin 

isolated from Amanita phalloides, binds at the interface between subunits in F-actin, locking adjacent subunits together and preventing depolymerization.

TLS Online TPP Program

#Id: 8335

#Unit 2. Cellular Organization

TLS Online TPP Program

#Id: 8336

#Unit 2. Cellular Organization

Actin filament treadmilling is accelerated by:

Profilin and Cofilin

TLS Online TPP Program

#Id: 8337

#Unit 2. Cellular Organization

Profilin – G-actin nucleotide exchange (ADP to ATP) 

Cofilin – F-actin disassembly

Thymosin B-4 – G-actin monomer sequestering

TLS Online TPP Program

#Id: 8338

#Unit 2. Cellular Organization

Profilin can bind proteins with sequences rich in proline residues at the same time it is bound to actin.

TLS Online TPP Program

#Id: 8339

#Unit 2. Cellular Organization

Filament capping proteins:

CapZ blocks (+)end Tropomodulin blocks (-)end