Solubilization of active receptors for VIP from guinea pig lung

The zwitterionic detergent 3-[(3-cholamidopropyl)dimethyl-ammonio]-1-propane sulfonate (CHAPS) was used to solubilize functional receptors for vasoactive intestinal peptide (VIP) from guinea pig lung. The binding of [125I]-VIP to the soluble receptors was time-dependent, reversible and saturable. Trypsin destroyed the activity of the receptors, indicating their proteinic nature. Dithiothreitol reduced the binding in a dose-dependent manner, suggesting the importance of disulfide bond(s) in receptor-binding activity. Binding of [125I]-VIP to the receptors was reversible and was competitively inhibited by unlabeled VIP, with 50% inhibition obtained at 305 nM VIP.