Jacobs D M, Yeh H, Price R M
Department of Microbiology, School of Medicine and Biomedical Sciences, State University of New York, Buffalo 14214.
Adv Exp Med Biol. 1990;256:233-45. doi: 10.1007/978-1-4757-5140-6_21.
The critical importance of the lipid A moiety of LPS in resistance and pathogenesis in gram negative infections has led to the assumption that LPS interaction with target cells is due to hydrophobic interaction with plasma membranes. However, work from several laboratories, including our own, is consistent with the presence of a cell membrane structure with characteristics of a "receptor". We have proposed a two-step model for LPS-membrane interaction which resolves the two views, and have developed a model system to control the first step (binding to membrane protein) and study the second step (intercalation into lipid bilayer). We examined the interaction of LPS with small unilamellar phosphatidylcholine vesicles labeled in the hydrophobic portion of the bilayer with the fluorescent probe diphenylhexatrine (DPH) and detected changes in the physical properties of the bilayer by measuring DPH fluorescence anisotropy (delta r). We have found that purified, phenol-extracted S. typhimurium LPS interacts with the bilayer as measured by an increase in delta r and conclude that the LPS aggregate coalesced with the lipid bilayer. The greatest change in delta r was achieved with lipid A, Ra-Re glycolipids and diphosphoryl lipid A. Monophosphoryl lipid A and lipid X were less effective. Preparations of wild-type LPS fractionated according to the length of the O-antigen side chain and unfractionated LPS had least effect on delta r. Thus other factors such as serum components or membrane proteins may be necessary to enhance the interaction of LPS with target cells.
脂多糖（LPS）的脂质A部分在革兰氏阴性菌感染的抵抗力和发病机制中至关重要，这使得人们认为LPS与靶细胞的相互作用是由于与质膜的疏水相互作用。然而，包括我们自己实验室在内的几个实验室的研究结果表明，存在一种具有“受体”特征的细胞膜结构。我们提出了一个两步模型来解释LPS与膜的相互作用，该模型解决了这两种观点，并开发了一个模型系统来控制第一步（与膜蛋白结合）并研究第二步（插入脂质双层）。我们研究了LPS与用荧光探针二苯基己三烯（DPH）标记在双层疏水部分的小单层磷脂酰胆碱囊泡的相互作用，并通过测量DPH荧光各向异性（δr）检测双层物理性质的变化。我们发现，通过δr的增加来衡量，纯化的、经苯酚提取的鼠伤寒沙门氏菌LPS与双层相互作用，并得出结论，LPS聚集体与脂质双层合并。脂质A、Ra-Re糖脂和二磷酸化脂质A导致δr的变化最大。单磷酸化脂质A和脂质X的效果较差。根据O抗原侧链长度分级的野生型LPS制剂和未分级的LPS对δr的影响最小。因此，可能需要血清成分或膜蛋白等其他因素来增强LPS与靶细胞的相互作用。
