Nicotinic pharmacophore: the pyridine N of nicotine and carbonyl of acetylcholine hydrogen bond across a subunit interface to a backbone NH.
Pharmacophore models for nicotinic agonists have been proposed for four decades. Central to these models is the presence of a cationic nitrogen and a hydrogen bond acceptor. It is now well-established that the cationic center makes an important cation-pi interaction to a conserved tryptophan, but the donor to the proposed hydrogen bond acceptor has been more challenging to identify. A structure of nicotine bound to the acetylcholine binding protein predicted that the binding partner of the pharmacophore's second component was a water molecule, which also hydrogen bonds to the backbone of the complementary subunit of the receptors. Here we use unnatural amino acid mutagenesis coupled with agonist analogs to examine whether such a hydrogen bond is functionally significant in the alpha4beta2 neuronal nAChR, the receptor most associated with nicotine addiction. We find evidence for the hydrogen bond with the agonists nicotine, acetylcholine, carbamylcholine, and epibatidine. These data represent a completed nicotinic pharmacophore and offer insight into the design of new therapeutic agents that selectively target these receptors.
Blum
Angela P
AP
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
Lester
Henry A
HA
Dougherty
Dennis A
DA
D000109:Acetylcholine / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001667:Binding, Competitive; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D002217:Carbachol / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D002244:Carbon / Q000737:chemistry / Q000378:metabolism; D005260:Female; D006860:Hydrogen Bonding; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008845:Microinjections; D008958:Models, Molecular; D015394:Molecular Structure; D009154:Mutation; D009538:Nicotine / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D018722:Nicotinic Agonists / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D009865:Oocytes / Q000378:metabolism / Q000502:physiology; D017434:Protein Structure, Tertiary; D011725:Pyridines / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D012333:RNA, Messenger / Q000008:administration & dosage / Q000235:genetics; D051381:Rats; D011978:Receptors, Nicotinic / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis
D019086:Bridged Bicyclo Compounds, Heterocyclic; D018722:Nicotinic Agonists; D011725:Pyridines; D012333:RNA, Messenger; D011978:Receptors, Nicotinic; C403531:nicotinic receptor alpha4beta2; D009538:Nicotine; D002244:Carbon; D002217:Carbachol; C082748:epibatidine; D000109:Acetylcholine; C023666:pyridine