One individual, however, expresses only a small number of these molecules—up to six different class I molecules and 12 or more different class II molecules.

TLS Online TPP Program

#Id: 9321

#Unit 4. Cell Communication and Cell Signaling

Low intracellular Ca2+ concentration is sensed by a class of Ca2+ -binding proteins known as guanylate cyclase–activating proteins.

TLS Online TPP Program

#Id: 9322

#Unit 4. Cell Communication and Cell Signaling

Guanylate cyclase–activating proteins, 

bind to guanylate cyclase and stimulate its activity, elevating cGMP level and causing the cGMP-gated ion channels to reopen.

TLS Online TPP Program

#Id: 9323

#Unit 4. Cell Communication and Cell Signaling

Terminate the visual response involves phosphorylation of activated (R*) rhodopsin, but not its dark (R) form

TLS Online TPP Program

#Id: 9324

#Unit 4. Cell Communication and Cell Signaling

Rhodopsin kinase, a member of the GRK family of kinases catalyzes phosphorylation of activated rhodopsin

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