Lys & Arg have four ionisations zones

1. 1--------pK1 – charge +2

2. pK1---------pK2 charge +1

3. pK2---------pKr charge 0

4. pKr---------14 charge -1

TLS Online TPP Program

#Id: 9325

#Unit 4. Cell Communication and Cell Signaling

Each opsin molecule has multiple principal serine and threonine phosphorylation sites on its cytosol-facing C-terminal segment.

TLS Online TPP Program

#Id: 9326

#Unit 4. Cell Communication and Cell Signaling

TLS Online TPP Program

#Id: 9327

#Unit 4. Cell Communication and Cell Signaling

The binding of arrestin to rhodopsin speeds up the inactivation process.

TLS Online TPP Program

#Id: 9328

#Unit 4. Cell Communication and Cell Signaling

Arrestin binds tightly to rhodopsin only when rhodopsin kinase has phosphorylated a sufficient number of C-terminal serines and threonines.

TLS Online TPP Program

#Id: 9329

#Unit 4. Cell Communication and Cell Signaling

The entire process of rhodopsin phosphorylation and its inactivation by arrestin is fast completed within 50ms. 

TLS Online TPP Program

#Id: 9330

#Unit 4. Cell Communication and Cell Signaling

Phosphorylated rhodopsin is restored to its light-sensitive state (R) during dark adaptation by a specific rhodopsin phosphatase