Which of the following statements about G-protein signaling pathways are true? Choose one or more:
A. The activated receptor causes the Ga and GBy subunits to covalently bind to one another.
B. GPCRs are peripheral membrane proteins, whereas their heterotrimeric G proteins are transmembrane proteins.
C. The Ga subunit activates by exchanging GDP for GTP,
D. When activated, both the Ga and the GBy subunits can modulate target proteins.
E. The ligand must bind to the G-protein-coupled receptor in order for the G protein to be activated.
