The tubulin subunit is a heterodimer formed from two closely related globular proteins called a-tubulin and b-tubulin.

TLS Online TPP Program

#Id: 8621

#Unit 2. Cellular Organization

The Cip/Kip family members bind to cyclin-bound CDKs and block the activity of cyclin D-, E-, A-, and B-containing complexes.

TLS Online TPP Program

#Id: 8622

#Unit 2. Cellular Organization

Cyclins are degraded through the action of two different E3-ligases:

1. SCF (Skp1, Cullin, and F-box proteins) 

2. APC/C or cyclosome

TLS Online TPP Program

#Id: 8623

#Unit 2. Cellular Organization

SCF and APC/C are multisubunit ubiquitin-protein ligases that belong to the RING finger family of ubiquitin-protein ligases.

TLS Online TPP Program

#Id: 8624

#Unit 2. Cellular Organization

TLS Online TPP Program

#Id: 8625

#Unit 2. Cellular Organization

Human SCF complexes contain: 

Three core components - Cul1 subunit, RBX1, Skp1 

and a substrate-targeting F-box protein

TLS Online TPP Program

#Id: 8626

#Unit 2. Cellular Organization

RBX1 is a RING finger–containing protein that binds the E2 ubiquitin-conjugating enzyme.