Negative membrane potential may allow calcium channels to be opened and permit calcium to enter the sperm. 

TLS Online TPP Program

#Id: 1538

#Unit 2. Cellular Organization

Keratins 

make up IF protein classes I and II 

found in epithelia

TLS Online TPP Program

#Id: 1539

#Unit 2. Cellular Organization

Class IV IF proteins compose the neurofilaments found in neurons

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.