Deactivating GPCRs is a very important process, allowing the termination of a signal. This is initiated by GRK, a kinase, which phosphorylates the GPCR. This prevents the G protein from binding to the GPCR, and recruits arrestin. This desensitises the GPCR.
The GPCR is then ingested into an endosome. The cell ensures the ligand has dissociated from the receptor, before removing arrestin and the phosphate groups. The GPCR is then inserted back into the membrane, allowing it to transduce signals again.
Arrestin blocks the G protein binding site of the GPCR, preventing the G protein from being activated.