Bellamy W R, Wakabayashi H, Takase M, Kawase K, Shimamura S, Tomita M
Nutritional Science Laboratory, Morinaga Milk Industry Co. Ltd, Zama City, Japan.
J Appl Bacteriol. 1993 Nov;75(5):478-84.
The antibacterial cell-binding properties of lactoferricin B, a potent bactericidal peptide derived from bovine lactoferrin, were investigated for the first time. To facilitate measurements of binding the peptide was radiolabelled by reduction and treatment with iodo-[1-14C]acetamide. 14C-lactoferricin B bound rapidly to the surface of Escherichia coli and Bacillus subtilis. The rate of binding was consistent with the rapid rate of killing caused by this peptide. The extent of binding was reduced in the presence of Mg2+ or Ca2+ ions which act to reduce its antimicrobial effectiveness. The optimal pH for binding was strain-dependent and the killing effect was maximal near the optimal pH for cell binding with each strain tested. These observations indicate that direct interaction of lactoferricin B with the cell surface is necessary for its lethal effect. The number of peptide molecules bound (> 10(6) per cell) was more than would be expected for binding to specific protein receptors. Lactoferricin B inhibited bacterial uptake of 3H-proline with effectiveness similar to polymyxin B, a known membrane-disruptive agent. The cell-binding event appears to lead to a disruption of normal permeability functions of the cytoplasmic membrane.
首次研究了乳铁传递蛋白B（一种源自牛乳铁蛋白的强效杀菌肽）的抗菌细胞结合特性。为便于测量结合情况，该肽通过用碘代-[1-¹⁴C]乙酰胺还原和处理进行放射性标记。¹⁴C-乳铁传递蛋白B迅速结合到大肠杆菌和枯草芽孢杆菌的表面。结合速率与该肽引起的快速杀伤速率一致。在Mg²⁺或Ca²⁺离子存在的情况下，结合程度降低，这些离子会降低其抗菌效果。结合的最佳pH值因菌株而异，并且在所测试的每个菌株中，杀伤效果在细胞结合的最佳pH值附近最大。这些观察结果表明，乳铁传递蛋白B与细胞表面的直接相互作用是其致死作用所必需的。结合的肽分子数量（每个细胞>10⁶个）超过了与特定蛋白质受体结合的预期数量。乳铁传递蛋白B抑制细菌对³H-脯氨酸的摄取，其效果与已知的膜破坏剂多粘菌素B相似。细胞结合事件似乎导致细胞质膜正常通透性功能的破坏。
