Which statement about G proteins is true?
A) G proteins contain only one important binding site.
B) When a G protein binds to an activated receptor protein,ADP is exchanged for ATP.
C) G protein-linked receptors are transmembrane proteins.
D) G proteins usually float free in the cytoplasm.
E) G proteins signal only the cell from which they are secreted.

Question

Quizplus · Accepted Answer

G protein-linked receptors are transmembrane proteins that bind to a specific ligand on the extracellular side and activate a G protein on the intracellular side of the membrane. G proteins are not free-floating in the cytoplasm and they can signal to neighboring cells in addition to the cell from which they are secreted. G proteins contain three important binding sites: one for GDP/GTP, one for the receptor, and one for downstream effector proteins. When a G protein binds to an activated receptor protein, GDP is exchanged for GTP, not ADP for ATP.

Which Statement About G Proteins Is True