Inhibitory Proteins in Cell Cycle-

Sic1 - Binds and inhibits S phase CDKs

CKIs p27, p57, and p21- Bind and inhibit CDKs

INK4 - Binds and inhibits G1 CDKs

Rb - Binds E2Fs

TLS Online TPP Program

#Id: 9045

#Unit 4. Cell Communication and Cell Signaling

Switching mechanism of monomeric G proteins 

“Off” state, Removal of the γ phosphate by GTPase-catalyzed hydrolysis causes switch I and switch II to relax into a different conformation

TLS Online TPP Program

#Id: 9046

#Unit 4. Cell Communication and Cell Signaling

Monomeric G proteins, including Ras and various Ras-like proteins, do not directly bind to receptors but act as intermediate proteins in signal transduction pathways.

TLS Online TPP Program

#Id: 9047

#Unit 4. Cell Communication and Cell Signaling

Monomeric G proteins are evolutionarily ancient, as evidenced by their widespread functions examples include: 

eIF2

EF1α and EF2

Ran

Sar

Rab

Rho, Rac, and Cdc42

TLS Online TPP Program

#Id: 9048

#Unit 4. Cell Communication and Cell Signaling

All G protein–coupled receptors contain seven transmembrane α-helical regions (H1–H7). In many GPCRs a short α helix H8 lies parallel to the membrane surface, and a covalently bound palmitic acid group

TLS Online TPP Program

#Id: 9049

#Unit 4. Cell Communication and Cell Signaling

Three principal classes of G PCR that bind their ligand in different ways:

TLS Online TPP Program

#Id: 9050

#Unit 4. Cell Communication and Cell Signaling

Member of family A of GPCRs -β-adrenergic receptors

Member of family B of GPCRs -glucagon receptor 

Member of family C of GPCRs -glutamate receptor