. Author manuscript; available in PMC: 2012 Jun 21.

Published in final edited form as: J Recept Signal Transduct Res. 2010 Oct;30(5):304–312. doi: 10.3109/10799893.2010.509728

Table 1.

Kinetics of diverse GPCR signaling systems measured by FRET.

Receptor	Association or activation(s)					Dissociation or deactivation(s)
Receptor	α_2AAR	β₁AR	α_2AR	M₁R	PTHR	α_2AAR	β₁AR	α_2AR	M₁R	PTHR
L + R ⇄LR	nd	nd	nd	nd	^Fast 0.17 ^Slow1.54	nd	nd	nd	nd	^Fast 1.40 ^Slow 28.00
LR ⇄LR*	0.045	0.060	0.066	< 0.100	1.59	2.00	2.50	4.00	0.20	58.00
LR* + G ⇄LR*G	0.045	0.060	0.050	0.200	1.58	≈ 10	8	15	3.70	48.00
G ⇄G*	≈1.00	0.450	0.450	2.00	2.04	38	15	37	35.00	121

Values represent the time constant (τ).

FRET, Förster resonance energy transfer; GPCR, G protein-coupled receptors; nd, not determined; PTHR, parathyroid hormone type 1 receptor. Ligand (L) and receptor (R) association and dissociation (L + R ⇄LR); receptor activation and deactivation (LR ⇄LR*); receceptor and G protein (G) interaction (LR* + G ⇄LR* G); G activation and deactivation (G ⇄G*). Reactions were recorded from live cells at a saturating concentration of an agonist: PTHrP(1–36) for PTHR; NE for α_2AAR and β₁AR; adenosine for A_2AR; oxotremodine-methiodide for M₁R.