Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Australia.
Antioxid Redox Signal. 2011 Jan 1;14(1):87-95. doi: 10.1089/ars.2009.3068. Epub 2010 Aug 20.
α-Conotoxins are peptides isolated from the venom ducts of cone snails that target nicotinic acetylcholine receptors (nAChRs). They are valuable pharmacological tools and have potential applications for treating a range of conditions in humans, including pain. However, like all peptides, conotoxins are susceptible to degradation, and to enhance their therapeutic potential it is important to elucidate the factors contributing to instability and to develop approaches for improving stability. AuIB is a unique member of the α-conotoxin family because the nonnative "ribbon" disulfide isomer exhibits enhanced activity at the nAChR in rat parasympathetic neurons compared with the native "globular" isomer. Here we show that the ribbon isomer of AuIB is also more resistant to disulfide scrambling, despite having a nonnative connectivity and flexible structure. This resistance to disulfide scrambling does not correlate with overall stability in serum because the ribbon isomer is degraded in human serum more rapidly than the globular isomer. Cyclization via the joining of the N- and C-termini with peptide linkers of four to seven amino acids prevented degradation of the ribbon isomer in serum and stabilized the globular isomers to disulfide scrambling. The linker length used for cyclization strongly affected the relative proportions of the disulfide isomers produced by oxidative folding. Overall, the results of this study provide important insights into factors influencing the stability and oxidative folding of α-conotoxin AuIB and might be valuable in the design of more stable antagonists of nAChRs.
α- 芋螺毒素是从芋螺毒液管中分离出来的肽类物质，靶向烟碱型乙酰胆碱受体 (nAChRs)。它们是有价值的药理学工具，在治疗人类的一系列疾病方面具有应用潜力，包括疼痛。然而，与所有肽类一样，芋螺毒素容易降解，为了提高其治疗潜力，阐明导致不稳定性的因素并开发改善稳定性的方法非常重要。AuIB 是 α-芋螺毒素家族中的一个独特成员，因为非天然的“带状”二硫键异构体在大鼠副交感神经元中的 nAChR 上表现出比天然“球形”异构体更高的活性。在这里，我们表明 AuIB 的带状异构体对二硫键重排也更具抗性，尽管其具有非天然的连接性和灵活的结构。这种对二硫键重排的抗性与血清中的整体稳定性无关，因为带状异构体在人血清中的降解速度比球形异构体更快。通过将 N-和 C-末端与四到七个氨基酸的肽接头连接进行环化，防止了血清中带状异构体的降解，并稳定了球形异构体以抵抗二硫键重排。用于环化的接头长度强烈影响氧化折叠产生的二硫键异构体的相对比例。总的来说，这项研究的结果为影响 α-芋螺毒素 AuIB 的稳定性和氧化折叠的因素提供了重要的见解，并可能在设计更稳定的 nAChR 拮抗剂方面具有价值。
