Koo Young Sook, Kim Jung Min, Park In Yup, Yu Byung Jo, Jang Su A, Kim Key-Sun, Park Chan Bae, Cho Ju Hyun, Kim Sun Chang
Department of Biological Sciences, Korea Advanced Institute of Science and Technology, 335 Gwahangno, Yuseong-gu, Daejeon 305-701, Republic of Korea.
Peptides. 2008 Jul;29(7):1102-8. doi: 10.1016/j.peptides.2008.02.019. Epub 2008 Mar 7.
The structure-activity relations and mechanism of action of parasin I, a 19-amino acid histone H2A-derived antimicrobial peptide, were investigated. Parasin I formed an amphipathic alpha-helical structure (residues 9-17) flanked by two random coil regions (residues 1-8 and 18-19) in helix-promoting environments. Deletion of the lysine residue at the N-terminal [Pa(2-19)] resulted in loss of antimicrobial activity, but did not affect the alpha-helical content of the peptide. The antimicrobial activity was recovered when the lysine residue was substituted with another basic residue, arginine ([R(1)]Pa), but not with polar, neutral, or acidic residues. Progressive deletions from the C-terminal [Pa(1-17), Pa(1-15)] slightly increased the antimicrobial activity (1-4 microg/ml) without affecting the alpha-helical content of the peptide. However, further deletion [Pa(1-14)] resulted in nearly complete loss of antimicrobial activity and alpha-helical structure. Confocal microscopic analysis and membrane permeabilization assays showed that parasin I and its analogs with comparable antimicrobial activities localized to the cell membrane and subsequently permeabilized the outer and cytoplasmic membranes. Pa(1-14) also localized to the cell membrane, but lost membrane-permeabilizing activity, whereas Pa(2-19) showed poor membrane-binding and -permeabilizing activities. The results indicate that the basic residue at the N-terminal is essential for the membrane-binding activity of parasin I, and among the membrane-binding parasin I analogs, the alpha-helical structure is necessary for the membrane-permeabilizing activity.
研究了19个氨基酸的组蛋白H2A衍生抗菌肽parasin I的构效关系及作用机制。在促进螺旋形成的环境中，parasin I形成了一个两亲性α-螺旋结构（残基9 - 17），两侧为两个无规卷曲区域（残基1 - 8和18 - 19）。N端赖氨酸残基缺失[Pa(2 - 19)]导致抗菌活性丧失，但不影响该肽的α-螺旋含量。当赖氨酸残基被另一个碱性残基精氨酸取代时（[R(1)]Pa），抗菌活性得以恢复，但被极性、中性或酸性残基取代时则不能恢复。从C端进行逐步缺失[Pa(1 - 17), Pa(1 - 15)]，在不影响该肽α-螺旋含量的情况下，抗菌活性略有增加（1 - 4微克/毫升）。然而，进一步缺失[Pa(1 - 14)]导致抗菌活性和α-螺旋结构几乎完全丧失。共聚焦显微镜分析和膜通透性测定表明，parasin I及其具有相当抗菌活性的类似物定位于细胞膜，随后使外膜和细胞质膜通透性增加。Pa(1 - 14)也定位于细胞膜，但失去了膜通透活性，而Pa(2 - 19)表现出较差的膜结合和膜通透活性。结果表明，N端的碱性残基对parasin I的膜结合活性至关重要，在具有膜结合活性的parasin I类似物中，α-螺旋结构对膜通透活性是必需的。
