In humans,

Only one of the follicles in one ovary starts to grow rapidly and becomes the dominant follicle, while the others regress, forming atretic follicles.

TLS Online TPP Program

#Id: 1540

#Unit 2. Cellular Organization

Kinesin-13 (End-Binding Proteins)

• A member of the kinesin motor protein superfamily

• These proteins are ATPases

 

TLS Online TPP Program

#Id: 1541

#Unit 2. Cellular Organization

Kinesin-13 (End-Binding Proteins)

• Bind and curve the end of the tubulin protofilaments into the GDP-β-tubulin conformation

• Facilitate the removal of terminal tubulin dimers 

• Greatly enhancing the frequency of catastrophes

TLS Online TPP Program

#Id: 1542

#Unit 2. Cellular Organization

Op18/stathmin (End-Binding Proteins) binds selectively to curved protofilaments and enhances terminal tubulin heterodimer dissociation from a microtubule end. 

 

TLS Online TPP Program

#Id: 1543

#Unit 2. Cellular Organization

Stathmin decreases the effective concentration of tubulin subunits that are available for polymerization (an action analogous to the drug colchicine) and enhances that a growing microtubule will switch to the shrinking state.

TLS Online TPP Program

#Id: 1544

#Unit 2. Cellular Organization

Phosphorylation of stathmin inhibits its binding to tubulin.

TLS Online TPP Program

#Id: 1545

#Unit 2. Cellular Organization

Katanin promotes breakage by extracting tubulin subunits from the wall of the microtubule (also releases microtubules from MTOCs).