In the presence of ATP,  myosin head releases from the actin filament. 

TLS Online TPP Program

#Id: 9076

#Unit 4. Cell Communication and Cell Signaling

A G protein– coupled receptor kinase phosphorylates serine and threonine residues in the

cytoplasmic segments of activated GPCRs

TLS Online TPP Program

#Id: 9077

#Unit 4. Cell Communication and Cell Signaling

β-Arrestin (Arr) binds to these phosphorylated receptors. Clathrin and AP2, two other proteins bound by β-arrestin, promote endocytosis of the receptor.

TLS Online TPP Program

#Id: 9078

#Unit 4. Cell Communication and Cell Signaling

GRK–β-arrestin pathway, suppress signaling by GPCRs, actually functions as a switch, turning off signaling by G proteins and turning on other signaling pathways.

TLS Online TPP Program

#Id: 9079

#Unit 4. Cell Communication and Cell Signaling

Muscarinic acetylcholine receptors coupled to a Gαi protein & found in cardiac muscles. 

TLS Online TPP Program

#Id: 9080

#Unit 4. Cell Communication and Cell Signaling

Binding of acetylcholine triggers the opening of an associated K+ channel  in the plasma membrane via the Gβγ subunit of a Gi protein

TLS Online TPP Program

#Id: 9081

#Unit 4. Cell Communication and Cell Signaling

The increase in K+ permeability hyperpolarizes the membrane, which reduces the frequency of heart muscle contraction.