Design of salt-insensitive glycine-rich antimicrobial peptides with cyclic tricystine structures.
Design of salt-insensitive glycine-rich antimicrobial peptides with cyclic tricystine structures.
复制标题
具有环状三胱氨酸结构的盐不敏感富含甘氨酸的抗菌肽的设计。
作者：
Tam,JP;Lu,YA;Yang,JL
使用环状肽主链和胱氨酸约束来开发具有广泛活性的盐不敏感抗菌肽 [Gly6]ccTP1a，该肽在 18 个残基序列中具有 8 个甘氨酸残基。在基于鲎素（一种已知的 β 链抗菌肽）的两个肽系列中检查了环状和胱氨酸限制所赋予的刚性和两亲性的重要性。第一个系列保留了鲎素的电荷和疏水性氨基酸，但包含零到四个共价约束，包括环状三胱氨酸鲎素 (ccTP1)。以平行系列制备相应的[Gly6]类似物，其序列中的所有六个大疏水氨基酸均被Gly取代。圆二色性测量表明，ccTP1 和 [Gly6]ccTP1a 表现出有序的 β-折叠结构，而受约束较少的 [Gly6] 类似物则呈无序状态。除了在高盐条件下测定的线性肽外，构象限制增加或减少的肽保留了广泛的活性谱，与鲎素相比，效力变化较小，为 2−10 倍。相比之下，甘氨酸替代类似物导致活性谱的巨大变化和效力的显着降低，这与构象限制的降低大致相关。除了针对大肠杆菌之外，具有两个或更少共价约束的富含甘氨酸的类似物在高盐条件下基本上没有活性。值得注意的是，在低盐和高盐测定中，最受限制的 [Gly6]ccTP1 对所有 10 种测试微生物都保留了广泛的活性谱。总的来说，我们的结果表明 [Gly6]ccTP1a 可以作为进一步类似物研究的模板，通过疏水性或非天然氨基酸的单个或多个替换来提高效力和特异性。
Cyclic peptide backbone and cystine constraints were used to develop a broadly active salt-insensitive antimicrobial peptide [Gly6]ccTP1awith eight Gly residues in an 18-residue sequence. The importance of rigidity and amphipathicity imparted by the cyclic and cystine constraints was examined in two peptide series based on tachyplesin, a known β-stranded antimicrobial peptide. The first series, which retained the charge and hydrophobic amino acids of tachyplesin, but contained zero to four covalent constraints, included a cyclic tricystine tachyplesin (ccTP1). Corresponding [Gly6] analogues were prepared in a parallel series with all six bulky hydrophobic amino acids in their sequences replaced with Gly. Circular dichroism measurements showed that ccTP1and [Gly6]ccTP1aexhibited well-ordered β-sheet structures, while the less constrained [Gly6] analogues were disordered. Except for linear peptides assayed under high-salt conditions, peptides with increased or decreased conformational constraints retained broad activity spectra with small variations in potency of 2−10-fold compared to that of tachyplesin. In contrast, Gly replacement analogues resulted in large variations in activity spectra and significant decreases in potency that roughly correlated with the decreases in conformational constraints. Except againstEscherichia coli, the Gly-rich analogues with two or fewer covalent constraints were largely inactive under high-salt conditions. Remarkably, the most constrained [Gly6]ccTP1aretained a broad activity spectrum against all 10 test microbes in both low- and high-salt assays. Collectively, our results show that [Gly6]ccTP1acould serve as a template for further analogue study to improve potency and specificity through single or multiple replacements of hydrophobic or unnatural amino acids.