Structure and allosteric activity of a single-disulfide conopeptide from Conus zonatus at human α3β4 and α7 nicotinic acetylcholine receptors.
Conopeptides are neurotoxic peptides in the venom of marine cone snails and have broad therapeutic potential for managing pain and other conditions. Here, we identified the single-disulfide peptides Czon1107 and Cca1669 from the venoms of Conus zonatus and Conus caracteristicus, respectively. We observed that Czon1107 strongly inhibits the human α3β4 (IC50 15.7 ± 3.0 μm) and α7 (IC50 77.1 ± 0.05 μm) nicotinic acetylcholine receptor (nAChR) subtypes, but the activity of Cca1669 remains to be identified. Czon1107 acted at a site distinct from the orthosteric receptor site. Solution NMR experiments revealed that Czon1107 exists in equilibrium between conformational states that are the result of a key Ser4-Pro5 cis-trans isomerization. Moreover, we found that the X-Pro amide bonds in the inter-cysteine loop are rigidly constrained to cis conformations. Structure-activity experiments of Czon1107 and its variants at positions P5 and P7 revealed that the conformation around the X-Pro bonds (cis-trans) plays an important role in receptor subtype selectivity. The cis conformation at the Cys6-Pro7 peptide bond was essential for α3β4 nAChR subtype allosteric selectivity. In summary, we have identified a unique single-disulfide conopeptide with a noncompetitive, potentially allosteric inhibitory mechanism at the nAChRs. The small size and rigidity of the Czon1107 peptide could provide a scaffold for rational drug design strategies for allosteric nAChR modulation. This new paradigm in the "conotoxinomic" structure-function space provides an impetus to screen venom from other Conus species for similar, short bioactive peptides that allosterically modulate ligand-gated receptor function.
['Mohan|Madhan Kumar|MK|0000-0002-5498-7280', 'Abraham|Nikita|N|', 'R P|Rajesh|R|0000-0003-0058-247X', 'Jayaseelan|Benjamin Franklin|BF|', 'Ragnarsson|Lotten|L|', 'Lewis|Richard J|RJ|', 'Sarma|Siddhartha P|SP|0000-0001-7619-8904']
D000494:Allosteric Regulation D000818:Animals D019556:COS Cells D002522:Chlorocebus aethiops D052078:Conus Snail D004220:Disulfides D057809:HEK293 Cells D006801:Humans D009498:Neurotoxins D010455:Peptides D011978:Receptors, Nicotinic D013329:Structure-Activity Relationship D064569:alpha7 Nicotinic Acetylcholine Receptor
single-disulfide conopeptides nicotinic acetylcholine receptors (nAChR) allosteric modulation allosteric regulation conformational exchange disulfide molecular pharmacology nAChR receptor antagonists neuropeptide nuclear magnetic resonance (NMR) peptide conformation proline cis/trans isomerism