Protein-ligand interactions: interaction of nitrosamines with nicotinic acetylcholine receptor.

Fluorimetry and spectrophotometry have been used to study the binding of dimethyl, dipropyl, dibutyl and diphenylnitrosamine to nicotinic acetylcholine receptor isolated, and purified, from Torpedo fuscomaculata. Scatchard analysis indicates that all four ligands are true agonists of the receptor exhibiting positive cooperative binding with the existence of more than one class of binding site. The number of binding sites for the nitrosamines approximates 2. Diphenylnitrosamine binds to the receptor more tightly at low concentrations (Kd1 = 1.3 microM) than the aliphatic nitrosamine (Kd1 = 8-12 microM). Yet at high concentrations all nitrosamines behaved with similar Kd values (27-38 microM).