Properties of a Putative Muscarinic Choltnergic Receptor From Drosophila Melanogaster

The powerful muscarinic antagonist [3H]quinuclidinyl benzilate (QNB) specifically binds to homogenates of Drosophila melanogaster head at a level of 65 ± 6 fmol/mg protein, with an apparent dissociation constant of 0.15–0.7 nM. The half‐life of the ligand‐receptor complex at 25°C is 30–40 min. Binding is inhibited by low concentrations of muscarinic ligands but not by low concentrations of nicotinic ligands, anticholinesterases or non‐cholinergic drugs. Binding‐sites are membrane bound and are inactivated by trypsin and by Triton X‐100. Part of the activity (<20%) is released into a high speed supernatant by 2 M‐NaCI. The gene coding for the putative muscarinic receptor in Drosophila is apparently not located adjacent to the gene for acetylcholinesterase