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.

中文翻译：

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圆锥状锥状单二硫键合肽对人α3β4和α7烟碱乙酰胆碱受体的结构和变构活性。

肽是海洋锥蜗牛毒液中的神经毒性肽，具有治疗疼痛和其他病症的广泛治疗潜力。在这里，我们从Conus zonatus和Conus caracteristicus的毒液中分别鉴定了单二硫键肽Czon1107和Cca1669。我们观察到Czon1107强烈抑制人α3β4（IC50 15.7±3.0μm）和α7（IC50 77.1±0.05μm）烟碱乙酰胆碱受体（nAChR）亚型，但Cca1669的活性仍有待确定。Czon1107在不同于正构受体位点的位点起作用。溶液NMR实验表明，Czon1107处于构象状态之间的平衡状态，这是关键的Ser4-Pro5顺反异构化的结果。此外，我们发现半胱氨酸间环中的X-Pro酰胺键被严格限制为顺式构象。Czon1107及其变体在位置P5和P7的结构活性实验表明，X-Pro键（顺式-反式）周围的构象在受体亚型选择性中起重要作用。Cys6-Pro7肽键处的顺式构象对于α3β4nAChR亚型变构选择性至关重要。总之，我们在nAChRs处鉴定了一种具有非竞争性，潜在变构抑制机制的独特单二硫键共肽。Czon1107肽的小尺寸和刚性可以为变构nAChR调节的合理药物设计策略提供一个支架。“ conotoxinomic”结构功能空间中的这一新范式为从别的Conus物种中筛选毒液寻找类似的，短的，可变构调节配体门控受体功能的生物活性肽提供了动力。