Structural implications of placing cationic residues at either the NH2- or COOH-terminus in a pore-forming synthetic peptide
Structural implications of placing cationic residues at either the NH2- or COOH-terminus in a pore-forming synthetic peptide
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DOI：
10.1007/s00232-002-1027-3
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发表时间：
2002-11-15
影响因子：
2.4
通讯作者：
Mitchell, K
中科院分区：
文献类型：
--
作者：
Broughman, JR;Shank, LP;Mitchell, K
通过引入由通道形成肽形成的阴离子选择孔来恢复氯离子电导，已被假设为囊性纤维化患者的一种新的治疗方式。在没有有机溶剂的情况下，从水环境中传递这些多肽是至关重要的。M2GlyR多肽是基于甘氨酸受体设计的，插入到脂质双层和极化的上皮细胞中，并自发组装到氯离子传导孔中。在末端添加4个赖氨酸残基增加了M2GlyR多肽的溶解度。膜内螺旋的两种取向都形成了阴离子选择性孔，但在溶解度、缔合和通道形成活性方面存在差异。为了确定赖氨酸残基的位置对这些性质的影响，利用化学交联、核磁共振和分子模拟研究了赖氨酸修饰的多肽的结构特征。α-螺旋肽的初始模型结构预测，COOH末端的赖氨酸残基通过折叠回来与肽螺旋片段上残基的主干羰基和羟基侧链形成氢键，从而形成封顶结构。相反，NH2末端的赖氨酸残基形成的氢键较少，并远离螺旋主干。核磁共振和化学交联的结果支持模型结构。赖氨酸残基的氢键形成的C-帽可能解释了NH2-末端和COOH-末端修饰的M2GlyR多肽的不同生物物理性质。
Restoration of chloride conductance via introduction of an anion-selective pore, formed by a channel-forming peptide, has been hypothesized as a novel treatment modality for patients with cystic fibrosis. Delivery of these peptides from an aqueous environment in the absence of organic solvents is paramount. M2GlyR peptides, designed based on the glycine receptor, insert into lipid bilayers and polarized epithelial cells and assemble spontaneously into chloride-conducting pores. Addition of 4 lysine residues to either terminus increases the solubility of M2GlyR peptides. Both orientations of the helix within the membrane form an anion-selective pore, however, differences in solubility, associations and channel-forming activity are observed. To determine how the positioning of the lysine residues affects these properties, structural characteristics of the lysyl-modified peptides were explored utilizing chemical cross-linking, NMR and molecular modeling. Initial model structures of the alpha-helical peptides predict that lysine residues at the COOH-terminus form a capping structure by folding back to form hydrogen bonds with backbone carbonyl groups and hydroxyl side chains of residues in the helical segment of the peptide. In contrast, lysine residues at the NH2-terminus form fewer H-bonds and extend away from the helical backbone. Results from NMR and chemical cross-linking support the model structures. The C-cap formed by H-bonding of lysine residues is likely to account for the different biophysical properties observed between NH2- and COOH-terminal-modified M2GlyR peptides.