Li Xia, Li Yifeng, Peterkofsky Alan, Wang Guangshun
Structure-Fun Laboratory, Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, USA.
Biochim Biophys Acta. 2006 Sep;1758(9):1203-14. doi: 10.1016/j.bbamem.2006.03.032. Epub 2006 Apr 7.
Aurein 1.2 is an antimicrobial and anticancer peptide isolated from an Australian frog. To improve our understanding of the mechanism of action, two series of peptides were designed. The first series includes the N-terminal membrane anchor of bacterial glucose-specific enzyme IIA, aurein 1.2, and a newly identified aurein 1.2 analog from human LL-37 (LLAA). The order of antibacterial activity is LLAA>aurein 1.2>>the membrane anchor (inactive). The structure of LLAA in detergent micelles was determined by (1)H NMR spectroscopy, including structural refinement by natural abundance (13)C(alpha), (13)C(beta), and (15)N chemical shifts. The hydrophobic surface area of the 3D structure is related to the retention time of the peptide on a reverse-phase HPLC column. The higher activity of LLAA compared to aurein 1.2 was attributed to additional cationic residues that enhance the membrane perturbation potential. The second peptide series was created by changing the C-terminal phenylalanine (F13) of aurein 1.2 to either phenylglycine or tryptophan. A closer or further location of the aromatic rings to the peptide backbone in the mutants relative to F13 is proposed to cause a drop in activity. Phenylglycine with unique chemical shifts may be a useful NMR probe for structure-activity relationship studies of antimicrobial peptides. To facilitate potential future use for NMR studies, random-coil chemical shifts for phenylglycine (X) were measured using the synthetic peptide GGXGG. Aromatic rings of phenylalanines in all the peptides penetrated 2-5 A below the lipid head group and are essential for membrane targeting as illustrated by intermolecular peptide-lipid NOE patterns.
奥瑞因1.2是一种从澳大利亚青蛙中分离出来的抗菌抗癌肽。为了更好地理解其作用机制，设计了两个系列的肽。第一个系列包括细菌葡萄糖特异性酶IIA的N端膜锚定序列、奥瑞因1.2以及从人LL-37中新鉴定出的奥瑞因1.2类似物（LLAA）。抗菌活性顺序为LLAA>奥瑞因1.2>>膜锚定序列（无活性）。通过（1）H NMR光谱确定了LLAA在去污剂胶束中的结构，包括通过天然丰度（13）C（α）、（13）C（β）和（15）N化学位移进行结构优化。三维结构的疏水表面积与肽在反相HPLC柱上的保留时间相关。LLAA比奥瑞因1.2活性更高归因于额外的阳离子残基增强了膜扰动潜力。第二个肽系列是通过将奥瑞因1.2的C端苯丙氨酸（F13）替换为苯甘氨酸或色氨酸而产生的。相对于F13，突变体中芳香环与肽主链的位置更近或更远被认为会导致活性下降。具有独特化学位移的苯甘氨酸可能是抗菌肽构效关系研究的有用NMR探针。为便于未来进行NMR研究，使用合成肽GGXGG测量了苯甘氨酸（X）的无规卷曲化学位移。所有肽中苯丙氨酸的芳香环穿透脂质头部基团下方2 - 5埃，分子间肽 - 脂质NOE模式表明这对于膜靶向至关重要。
