If a FRET experiment was carried out with blue fluorescent protein attached to the $\alpha$ subunit of a stimulatory G-protein and a green fluorescent protein attached to the $\beta$ subunit, the presence of a strong FRET signal would be associated with:
A) interaction of a G protein-coupled receptor with an antagonist.
B) hydrolysis of GTP in the $\alpha$ subunit.
C) increased concentrations of cAMP.
D) both interaction of a G protein-coupled receptor with an antagonist and hydrolysis of GTP in the $\alpha$subunit.
E) both hydrolysis of GTP in the $\alpha$ subunit and increased concentrations of cAMP.

Question

Quizplus · Accepted Answer

FRET signal is inversely proportional to the distance between the two fluorescent proteins. When a G protein-coupled receptor interacts with an antagonist, the G protein is not activated and the F1F1F1S1F1F1F10 subunit does not bind GTP. As a result, the F1F1F1S1F1F1F10 subunit remains bound to the F1F1F1S1F1F1F10 subunit, and the distance between the two fluorescent proteins is small, resulting in a strong FRET signal.

If a FRET Experiment Was Carried Out with Blue Fluorescent α\alphaα

If a FRET Experiment Was Carried Out with Blue Fluorescent $\alpha$