Fig. 5.

The effect of GppNHp on secretin radioligand binding to dimeric and monomeric secretin receptors. Shown are curves for secretin competing for binding of [¹²⁵I-Tyr¹⁰]secretin to membranes from COS cells expressing the dimeric (wild type, WT) and monomeric (G243A/I247A) secretin receptor constructs in the absence and presence of 10 μM GppNHp. Values represent percentages of maximal saturable binding that were observed in the absence of secretin. They are expressed as means ± S.E.M. of duplicate data from three independent experiments.