Structural location determines functional roles of the basic amino acids of KR-12, the smallest antimicrobial peptide from human cathelicidin LL-37.
Structural location determines functional roles of the basic amino acids of KR-12, the smallest antimicrobial peptide from human cathelicidin LL-37.
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DOI：
10.1039/c3ra42599a
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发表时间：
2013-11-14
期刊：
影响因子：
3.9
通讯作者：
Wang G
中科院分区：
文献类型：
--
作者：
Mishra B;Epand RF;Epand RM;Wang G
阳离子抗菌肽是公认的开发新一代抗菌剂以对抗超级细菌的模板。人cathelicidin LL-37是人天然免疫中必需的宿主防御分子。先前，我们鉴定KR-12为LL-37的最小抗菌肽。KR-12具有窄的活性谱，因为它对革兰氏阴性大肠杆菌有活性，但对革兰氏阳性金黄色葡萄球菌没有活性。然而，KR-12的碱性氨基酸的功能作用尚未阐明。KR-12的阳离子氨基酸的丙氨酸扫描为它们在肽的活性中的不同作用提供了证据。细菌杀伤和膜渗透实验表明，R23 A和K25 A突变体，以及赖氨酸-精氨酸突变体，比KR-12更有效。另外三个阳离子残基（K18，R19，和R29）的KR-12，这是位于两亲螺旋的亲水面，似乎是更重要的聚集阴离子脂质或溶血比R23和K25在界面区域。虽然界面R23或K25的损失降低了肽螺旋度，强调了其在膜结合中的重要作用，但KR-12的肽活性的总体增加可归因于肽疏水性的增加，其在这种情况下超过了碱性电荷的作用。相反，界面R23或K25的突变降低了GF-17的肽杀菌活性，GF-17是一种重叠的、更疏水的和有效的肽，也衍生自LL-37。因此，肽的疏水环境决定了界面碱性残基的丙氨酸取代是否增加或减少膜渗透和肽活性。
Cationic antimicrobial peptides are recognized templates for developing a new generation of antimicrobials to combat superbugs. Human cathelicidin LL-37 is an essential host defense molecule in human innate immunity. Previously, we identified KR-12 as the smallest antibacterial peptide of LL-37. KR-12 has a narrow activity spectrum since it is active against Gram-negative Escherichia coli but not Gram-positive Staphylococcus aureus. The functional roles of the basic amino acids of KR-12, however, have not yet been elucidated. An alanine scan of cationic amino acids of KR-12 provided evidence for their distinct roles in the activities of the peptides. Bacterial killing and membrane permeation experiments indicate that the R23A and K25A mutants, as well as the lysine-to-arginine mutant, were more potent than KR-12. Another three cationic residues (K18, R19, and R29) of KR-12, which are located in the hydrophilic face of the amphiphathic helix, appeared to be more important in clustering anionic lipids or hemolysis than R23 and K25 in the interfacial region. While the loss of interfacial R23 or K25 reduced peptide helicity, underscoring its important role in membrane binding, the overall increase in peptide activity of KR-12 could be ascribed to the increased peptide hydrophobicity that outweighed the role of basic charge in this case. In contrast, the mutations of interfacial R23 or K25 reduced peptide bactericidal activity of GF-17, an overlapping, more hydrophobic and potent peptide also derived from LL-37. Thus, the hydrophobic context of the peptide determines whether an alanine substitution of an interfacial basic residue increases or decreases membrane permeation and peptide activity.