Concentration dependence of the covalent reaction at mutant receptors at the binding level.

Left column: mutated receptors. Middle column: homology of the mutations to α1. Right column EC50 is given as mean ±SD for three to four experiments where each point in the dose-response curve was determined in triplicates. The receptors were exposed to increasing concentrations of 3-NCS compound for 30 min on ice and extensively washed. Residual binding was determined using [3H]Ro15–1788 as radioactive ligand and converted to percentage of binding sites covalently reacted. All wild type receptors showed no covalent reaction. n.r.: no covalent reaction.a[3H]15–4513 was used as a radioactive ligand.