University of Calgary, Department of Biological Sciences, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada.
Biochem Cell Biol. 2012 Jun;90(3):362-77. doi: 10.1139/o11-057. Epub 2012 Jan 17.
Lactoferrin is an 80 kDa iron binding protein found in the secretory fluids of mammals and it plays a major role in host defence. An antimicrobial peptide, lactoferrampin, was identified through sequence analysis of bovine lactoferrin and its antimicrobial activity against a wide range of bacteria and yeast species is well documented. In the present work, the contribution of specific amino acid residues of lactoferrampin was examined to evaluate the role that they play in membrane binding and bilayer disruption. The structures of all the bovine lactoferrampin derivatives were examined with circular dichroism and nuclear magnetic resonance spectroscopy, and their interactions with phospholipids were evaluated with differential scanning calorimetry and isothermal titration calorimetry techniques. From our results it is apparent that the amphipathic N-terminal helix anchors the peptide to membranes with Trp 268 and Phe 278 playing important roles in determining the strength of the interaction and for inducing peptide folding. In addition, the N-terminal helix capping residues (DLI) increase the affinity for negatively charged vesicles and they mediate the depth of membrane insertion. Finally, the unique flexibility in the cationic C-terminal region of bovine lactoferrampin does not appear to be essential for the antimicrobial activity of the peptide.
乳铁蛋白是一种 80kDa 的铁结合蛋白，存在于哺乳动物的分泌液中，在宿主防御中起着重要作用。通过对牛乳铁蛋白的序列分析，鉴定出一种抗菌肽乳铁蛋白肽，其对多种细菌和酵母的抗菌活性已有文献记载。在本工作中，我们检查了乳铁蛋白肽中特定氨基酸残基的贡献，以评估它们在膜结合和双层破坏中所起的作用。用圆二色性和核磁共振波谱法研究了所有牛乳铁蛋白肽衍生物的结构，并通过差示扫描量热法和等温滴定量热法评估了它们与磷脂的相互作用。从我们的结果可以明显看出，两亲性的 N 端螺旋用色氨酸 268 和苯丙氨酸 278 将肽锚定在膜上，这两个残基在确定相互作用的强度和诱导肽折叠方面起着重要作用。此外，N 端螺旋封端残基（DLI）增加了对带负电荷的囊泡的亲和力，并介导了膜的插入深度。最后，牛乳铁蛋白肽阳离子 C 端区域的独特柔韧性似乎对肽的抗菌活性不是必需的。
