Role of disulfide bridges in the folding of conotoxins

描述（由申请方提供）：芋螺毒素是一种富含二硫键的小肽，具有区分各种类型离子通道的能力，使其成为表征神经元通路和药物开发的理想诊断工具。这个家庭的一个成员，？芋螺毒素MVIIA（齐考尼肽）最近被FDA批准用于治疗慢性疼痛。二硫键的作用的评估是必不可少的，在我们的蛋白质折叠的理解。该提案将探讨小肽序列中的微小变化（引入构象限制或改变分子内桥的大小）如何影响折叠特性。目标肽是α-芋螺毒素及其类似物;具有四个半胱氨酸残基的十三或十四个含氨基酸的肽酰胺。四个半胱氨酸可以形成两个二硫键，导致三种可能的区域异构体，其中只有一种在自然界中发现。氨基酸脯氨酸的环状性质可以对肽的折叠施加空间限制，导致对目标天然区域异构体的合成的更好的选择性。这项工作将集中在三个领域：㈠研究由于氨基酸序列的变化而引起的折叠变化，以及含有一种新氨基酸的芋螺毒素的合成和生物物理特性，这种新氨基酸是具有碱性侧链的脯氨酸样氨基酸，已被证明对增加生物活性至关重要。(ii)具有半胱氨酸同系物或内酰胺桥的结构的合成和生物物理表征。和（iii）建模（分子动力学和从头算）的分子参数，（S？S距离，侧链的旋转构象），与导致特定区域异构体的键形成的活化能相关。芋螺毒素是具有区分各种类型离子通道的能力的小肽，使其成为表征神经系统途径和药物开发的理想诊断工具。例如，Ziconitide（？-芋螺毒素MVIIA）已经被FDA批准用于治疗癌症和艾滋病患者的慢性疼痛。该提案旨在开发更有效地制造毒素的方法。

DESCRIPTION (provided by applicant): Conotoxins are small, disulfide-rich peptides having the ability to differentiate between various types of ion channels, making them ideal diagnostic tools in the characterization of neuronal pathways and in drug development. One member of this family, ?-conotoxin MVIIA (Ziconitide) was recently approved by the FDA for the treatment of chronic pain. Evaluation of the role of disulfide bridges is essential in our understanding of protein folding. This proposal will explore how slight changes (introducing conformational restrictions or altering the size of the intramolecular bridges) in the sequences of small peptides affect folding properties. The target peptides are a-conotoxins and their analogues; thirteen or fourteen amino acid-containing peptide amides having four cysteine residues. The four cysteines can form two disulfide bridges, leading to three possible regioisomers, only one of which is found in nature. The amino acid proline's cyclic nature may impose steric constraints for the folding of the peptides, resulting in much better selectivity for the synthesis of the target native regioisomers. The work will focus in three areas: (i) Study of the variation in folding due to changes in the amino acid sequence and synthesis and biophysical characterization of conotoxins that contain a novel amino acid, proline-like with a basic side chain, which has been proven to be essential for increased biological activity. (ii) Synthesis and biophysical characterization of structures with homologues of cysteine or with a lactam bridge. And (iii) modeling (molecular dynamics and ab initio) of the molecular parameters, (S?S distance, rotational conformation of the side chains), relevant to activation energy of the bond formation that results in a specific regioisomer. Conotoxins are small peptides having the ability to differentiate between various types of ion channels, making them ideal diagnostic tools in the characterization of nervous system pathways and in drug development. For instance, Ziconitide (?-conotoxin MVIIA) has already been approved by the FDA for cancer and AIDS patients for the treatment of chronic pain. This proposal aims to develop methods to make contoxins more efficiently.