Figure 4. Influence of aptamers on conformational changes conferred by ligands.

(a–d) Bimane fluorescence quenching measurement shows that aptamers A1, A2, and A13 stabilize active forms of β₂AR, while aptamer A16 stabilizes an inactive conformation. Bimane fluorescence quenching measurement detects conformational changes of the β₂AR via movement of a bimane probe on TM6 (at C265) upon the binding of agonists, (BI167107 [BI] or isoproterenol [ISO]) and/or aptamer: A1 (a), A2 (b), A13 (c) or A16 (d). Fluorescence emission spectra showing ligand-induced conformational changes of bimane-labeled β₂AR in the absence (black dashed line) or presence of full agonist (ISO, blue dashed line, or BI, red dashed line), inverse agonist ICI-118,551 (ICI, green dashed line), aptamer A1, A2, A13, or A16 (black solid line), or a combination of aptamer (A1, A2, A13, or A16) with ISO (blue solid line), BI (red solid line), or ICI (green solid line).