在抗菌肽的选择或设计中,阳离子氨基酸和链长对抑制效力和特异性所起的关键作用尚不清楚。使用化学合成的7至14个残基的L-Lys和L-Arg的同肽进行了基础研究。在不同浓度水平的广泛范围的革兰氏阳性细菌中评估了它们对生长抑制的影响。有趣的是,在较低的浓度(10μM),具有奇数个残基的Lys同肽,尤其是有11个残留物,显示出比具有偶数个残基的那些更广泛的抑制活性。在较高的肽浓度(>20μM),Lys同肽的抑制活性与链中残基的数量直接相关。相比之下,Arg同肽,在较低的浓度下,没有表现出与残留物数量相关的明确的细菌抑制模式;然而,在较高浓度(>20μM),抑制作用更为明显。浓度高达300μM的Lys同肽对CHSE-214细胞显示出明显较低的毒性。Arg同肽在低于100μM的浓度下表现出可忽略的细胞毒性,直至11个残基的链长,但是当肽链长度达到12个氨基酸残基和更高浓度时,毒性会突然增加。所有合成的同肽在缓冲液和脂质体中均显示出特征性的聚脯氨酸II螺旋构象,如CD光谱学所示。该结果表明,与Arg同肽相比,具有奇数残基(9和11)的短Lys同肽具有针对革兰氏阳性细菌细胞的广谱活性,这反过来又对这些细胞显示出相当高的选择性。通过研究Lys和Arg同肽之间的差异,这项研究有助于理解它们的生长抑制和选择性机制。因此,它为合理设计短抗微生物肽提供了进一步的指导。
In the selection or design of antimicrobial peptides, the key role played by cationic amino acids and chain length on the inhibitory potency and specificity is not clear. A fundamental study was conducted using chemically synthesized homopeptides of L-
Lys and L-Arg ranging from 7 to 14 residues. Their effect on growth inhibition was evaluated over a wide range of Gram-positive bacteria at different levels of concentration. Interestingly, at lower concentrations (10 μM),
Lys homopeptides with odd number of residues, especially with 11 residues, showed a broader inhibitory activity than those with even number of residues. At higher peptide concentrations (>20 μM), the inhibitory activity of
Lys homopeptides was directly related to the number of residues in the chain. In contrast, Arg homopeptides, at lower concentrations, did not exhibit a defined pattern of bacterial inhibition related to the number of residues; however, at higher concentrations (>20 μM), the inhibitory effects were more pronounced.
Lys homopeptides at concentrations up to 300 μM showed a remarkably lower toxicity against CHSE-214 cells. Arg homopeptides exhibited negligible cytotoxicity up to chain length of 11 residues at concentrations lower than 100 μM, but an abrupt increase in toxicity resulted when the peptide chain length reached 12 amino acid residues and higher concentrations. All synthesized homopeptides displayed characteristic polyproline II helix conformation in both buffer and liposomes, as shown by CD spectroscopy. This result suggests that short
Lys homopeptides with an odd number of residues (9 and 11) have a broad spectrum of activity against Gram-positive bacterial cells compared with Arg homopeptides, which in turn showed a considerably higher selectivity toward those cells. By investigating the differences between Lys and Arg homopeptides, this study contributes to the understanding of their mechanism of growth inhibition and selectivity. Thus, it provides further guidelines for a rational design of short antimicrobial peptides.