In the resting state, which describes the G-protein?

In the resting state, which describes the G-protein?

• A. GDP is bound to the alpha subunit and the subunits are fully separate.
• B. The alpha and beta-gamma subunits are bound to the receptor.
• C. GDP is bound to the beta subunit.
• D. The alpha and beta-gamma subunits are associated together, and GDP is bound to the alpha subunit.

Answer: (D)

In the resting state, the G protein exists as a heterotrimer composed of the alpha, beta, and gamma subunits. The alpha subunit carries GDP, and this alpha subunit remains bound to the beta-gamma dimer, forming a stable complex that is not yet actively signaling. Activation requires GDP to be exchanged for GTP on the alpha subunit, which then causes the alpha subunit to dissociate from the beta-gamma pair to regulate downstream effectors. So the description that best fits the resting state is that the alpha and beta-gamma subunits are associated together, and GDP is bound to the alpha subunit.

In the resting state, the G protein exists as a heterotrimer composed of the alpha, beta, and gamma subunits. The alpha subunit carries GDP, and this alpha subunit remains bound to the beta-gamma dimer, forming a stable complex that is not yet actively signaling. Activation requires GDP to be exchanged for GTP on the alpha subunit, which then causes the alpha subunit to dissociate from the beta-gamma pair to regulate downstream effectors. So the description that best fits the resting state is that the alpha and beta-gamma subunits are associated together, and GDP is bound to the alpha subunit.