Figure 5.

Changes in cell surface expression induced by mutations. A. The structural integrity of the GPCR fold is believed to be maintained by a network of non-covalent inter-helical contacts (described in²⁰), visualized here on the β₂AR structure. Disruption of this network can be expected to result in increased receptor instability. B. Mutations, increasing (green) or decreasing (red) receptor cell surface expression in at least two different receptors, are shown on the inactive structure of β₂AR. A, B. Left panel, side view; right panel, top view from the extra-cellular side; for the latter the ECL2 helix was removed for better visualization. The numbers of trans-membrane helices I–VII are indicated in gray circles.