Proline-rich antimicrobial peptides (PR-AMPs) having a potent antimicrobial activity predominantly toward Gram-negative bacteria and negligible toxicity toward host cells, are attracting attention as new templates for developing antibiotic drugs. We have previously isolated and characterized several bactenecins that are promising in this respect, from the leukocytes of the domestic goat Capra hircus: ChBac5, miniChBac7.5N-α, and -β, as well as ChBac3.4. Unlike the others, ChBac3.4 shows a somewhat unusual pattern of activities for a mammalian PR-AMP: it is more active against bacterial membranes as well as tumor and, to the lesser extent, normal cells. Here we describe a SAR study of ChBac3.4 (RFRLPFRRPPIRIHPPPFYPPFRRFL-NH2) which elucidates its peculiarities and evaluates its potential as a lead for antimicrobial or anticancer drugs based on this peptide. A set of designed structural analogues of ChBac3.4 was explored for antibacterial activity toward drug-resistant clinical isolates and antitumor properties. The N-terminal region was found to be important for the antimicrobial action, but not responsible for the toxicity toward mammalian cells. A shortened variant with the best selectivity index toward bacteria demonstrated a pronounced synergy in combination with antibiotics against Gram-negative strains, albeit with a somewhat reduced ability to inhibit biofilm formation compared to native peptide. C-terminal amidation was examined for some analogues, which did not affect antimicrobial activity, but somewhat altered the cytotoxicity toward host cells. Interestingly, non-amidated peptides showed a slight delay in their impact on bacterial membrane integrity. Peptides with enhanced hydrophobicity showed increased toxicity, but in most cases their selectivity toward tumor cells also improved. While most analogues lacked hemolytic properties, a ChBac3.4 variant with two additional tryptophan residues demonstrated an appreciable activity toward human erythrocytes. The variant demonstrating the best tumor/nontumor cell selectivity was found to more actively initiate apoptosis in target cells, though its action was slower than that of the native ChBac3.4. Its antitumor effectiveness was successfully verified in vivo in a murine Ehrlich ascites carcinoma model. The obtained results demonstrate the potential of structural modification to manage caprine bactenecins’ selectivity and activity spectrum and confirm that they are promising prototypes for antimicrobial and anticancer drugs design.

作为开发抗生素药物的新模板，富含脯氨酸的抗菌肽（PR-AMPs）主要对革兰氏阴性菌具有强大的抗菌活性，而对宿主细胞的毒性却可以忽略不计。我们以前从家山羊的白细胞中分离并鉴定了几种在这方面很有前途的细菌素卡普拉岛：ChBac5，miniChBac7.5N-α和-β，以及ChBac3.4。与其他化合物不同，ChBac3.4对于哺乳动物PR-AMP表现出某种不同寻常的活性模式：它对细菌膜和肿瘤更有活性，而对正常细胞的活性较小。在这里，我们描述了ChBac3.4（SARR）的SAR研究（RFRLPFRRPPIRIHPPPFYPPFRRFL-NH2），该研究阐明了其独特性并评估了其作为基于该肽的抗微生物或抗癌药物的潜力。探索了一组设计的ChBac3.4结构类似物，以针对耐药性临床分离株的抗菌活性和抗肿瘤特性。的ñ发现末端区域对于抗菌作用是重要的，但是对对哺乳动物细胞的毒性不负责。对细菌具有最佳选择性的缩短变体与抗革兰氏阴性菌株的抗生素联合使用具有明显的协同作用，尽管与天然肽相比，抑制生物膜形成的能力有所降低。C检查了末端酰胺化的某些类似物，这些类似物不影响抗微生物活性，但在一定程度上改变了对宿主细胞的细胞毒性。有趣的是，未酰胺化的肽对细菌膜完整性的影响略有延迟。具有增强的疏水性的肽显示出增加的毒性，但是在大多数情况下，它们对肿瘤细胞的选择性也有所提高。虽然大多数类似物缺乏溶血特性，但带有两个其他色氨酸残基的ChBac3.4变体对人红细胞表现出明显的活性。发现表现出最佳肿瘤/非肿瘤细胞选择性的变异体可更积极地启动靶细胞的凋亡，尽管其作用比天然ChBac3.4慢。其抗肿瘤功效已成功验证体内在小鼠艾氏腹水癌模型中。获得的结果证明了结构修饰的潜力来管理山羊细菌素的选择性和活性谱，并证实它们是抗微生物和抗癌药物设计的有希望的原型。