摘要
Mammalian myeloid and epithelial cell express several antibacterial peptides (defensins and cathelicidins) that contribute to the innate host defense by killing invaded microorganisms. CAP11 (cationic antibacterial polypeptide of 11kDa), which was isolated from guinea pig neutrophils, has been shown to possess the potent bactericidal and LPS-neutralizing activities. CAP11 is a homodimer of Gly1-Ile43 joined with one disulfide bond. In this study, we revealed that the dimerization of the peptides is not essential for its biological activity, and 18mer peptide of CAP11(G1-R18) is the most potent among various peptide derivatives. However, its biological activities were much lower compared with native CAP11. Furthermore, we tried to enhance the biological activities of CAP11(G1-R18) by substituting amino acids. Two novel peptides, CAP11(1-18m) and CAP11(1-18m2), whose hydrophobicity and positive charge were modified by the amino acid substitutions, exhibited more potent bactericidal activities against S.aureus and E.coli, and more strongly inhibited the LPS-binding to CD14+ RAW264.7 cells, compared with CAP11; i.e. the bactericidal and LPS-neutralizing activities of CAP11(1-18m2) was about 10-fold greater than those of CAP11, and CAP11(1-18m2) completely killed both methicillin-sensitive S.aureus (MSSA) and methicillin-resistant S.aureus (MRSA) even at 0.1μg/ml.
Thus, the bactericidal and LPS-neutralizing activities of CAP11-derived antibacterial peptides could be enhanced by the modification of their hydrophobicity and positive charge via the amino acid substitutions.
摘要译文
哺乳动物髓细胞和上皮细胞表达多种抗菌肽（防御和cathelicidins）通过杀死侵入的微生物有助于先天宿主防御。CAP11（11kDa的阳离子抗菌多肽），这是从豚鼠嗜中性粒细胞中分离，已被证明具有强效的杀菌和内毒素中和活性。CAP11是Gly的二聚体SUP 1 / SUP -Ile SUP 43 / SUP加入了一个二硫键。在这项研究中，我们发现该肽的二聚化是不是其生物活性所必需的，和CAP11的18mer肽（G SUP 1 / SUP -R SUP 18 / SUP）是各种肽衍生物中最有力的。然而，随着本土CAP11相比，其生物活性均低得多。此外，我们试图提高CAP11的生物活性（G SUP 1 / SUP -R SUP 18 / SUP）通过置换氨基酸。两种新型肽，CAP11（1-18m）和CAP11（1-18m2）其疏水性和正电荷的氨基酸取代进行修饰，表现出对抗金黄色葡萄球菌及大肠杆菌更有效的杀菌活性，更强烈地抑制了LPS-结合CD14 SUP / SUP RAW264.7细胞，用CAP11比较;即CAP11（1-18m2）的杀菌和内毒素中和活性为约10倍高于CAP11的，和CAP11（1-18m2）完全杀死两甲氧西林敏感S.金黄色葡萄球菌（MSSA）和耐甲氧西林金黄色葡萄球菌（MRSA），甚至在0.1微克/毫升。\r
因此，CAP11衍生抗菌肽的杀菌和内毒素中和活性可以通过它们的疏水性的经由氨基酸取代的修饰和正电荷来增强。
Daiju Okuda[1]; Shin Yomogida[1]; Hiroshi Tamura[2];Isao Nagaoka[1]. Augmentation of the bactericidal and LPS-neutralizing activities of guinea pig cathelicidin CAP11-derived antimicrobial peptides by amino acid substitutions[J]. Inflammation and Regeneration, 2006,26(2): 101-106