Fig. 1.

Two-dimensional representation of the 5-HT4R sequence. Residues colored red were identified to undergo oxidation in footprinting experiments. The approximate membrane lipid bilayer is shown as solid gray blocks at both sides, and helices are represented as green cylinders. The sites of trypsin cleavages experimentally observed are shown as solid lines. Purple solid lines indicate exposed and expected cleavage sites; blue solid lines indicate juxtamembrane cleavage sites, and red solid lines indicate sites not accessible to trypsin. Seven residues with calculated oxidation rates by mass spectrometry are indicated by an asterisk around that residue.