AP BIOLOGY

Detailed explanation-1: -G proteins are molecular switches that are activated by receptor-catalyzed GTP for GDP exchange on the G protein alpha subunit, which is the rate-limiting step in the activation of all downstream signaling.

Detailed explanation-2: -As for Ras GTPases, G is “activated” for interaction with effectors when bound to GTP, and deactivated by its intrinsic GTPase activity – which, for most G proteins, is accelerated by GTPase activating proteins or protein domains (GAPs).

Detailed explanation-3: -Activation of the heterotrimeric G protein, Gi, results in ATP release from erythrocytes. This effect is may be related to the activity of beta subunits associated with this G protein in the human erythrocyte.