Ohtoyo T, Shimagaki M, Otoda K, Kimura S, Imanishi Y
Department of Polymer Chemistry, Kyoto University, Japan.
Biochemistry. 1988 Aug 23;27(17):6458-63. doi: 10.1021/bi00417a039.
Changes in membrane fluidity induced by lectin addition to 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) vesicles containing synthetic glycopeptides were measured by depolarization of the fluorescent probes 8-anilino-1-naphthalenesulfonate (ANS) and 1,6-diphenyl-1,3,5-hexatriene (DPH). In the present synthesized glycopeptides, N-acetylglucosamine (GlcNAc) and a tripeptide were connected by aliphatic chains of different lengths. A pyrenyl group, which is introduced to the peptide moiety, acted as a probe to characterize the distribution of glycopeptides in the membrane on the basis of its excimer formation. The glycopeptide was shown to be distributed to DPPC vesicles with the peptide moiety buried in the hydrophobic core of the lipid bilayer and the glyco moiety exposed to the outside of the membrane. By the addition of wheat germ agglutinin (WGA) to the vesicles containing the glycopeptides, intravesicular cross-linking of glycopeptides in the membrane and aggregation of vesicles were observed. The intravesicular cross-linking was antagonized by GlcNAc above the phase transition temperature. However, the dissociation of aggregation required the addition of a stronger antagonist, N,N'-diacetylchitobiose. The addition of the glycopeptide to DPPC vesicles above the phase transition temperature decreased the membrane fluidity. However, a succeeding addition of WGA caused a large increase of membrane fluidity at either the surface or the hydrophobic core of the lipid bilayer membrane. This increase of membrane fluidity was attributed to two factors by use of two kinds of antagonists having different potencies: one is a WGA-mediated cross-linking of glycopeptides in the membrane, and the other is a close contact of vesicles on aggregation.
通过荧光探针8-苯胺基-1-萘磺酸盐（ANS）和1,6-二苯基-1,3,5-己三烯（DPH）的去极化，测量了在含有合成糖肽的1,2-二棕榈酰-sn-甘油-3-磷酸胆碱（DPPC）囊泡中添加凝集素所诱导的膜流动性变化。在目前合成的糖肽中，N-乙酰葡糖胺（GlcNAc）和一个三肽通过不同长度的脂肪链相连。引入肽部分的芘基团作为探针，基于其激基缔合物的形成来表征糖肽在膜中的分布。结果表明，糖肽分布在DPPC囊泡中，肽部分埋在脂质双层的疏水核心中，而糖部分暴露在膜的外侧。向含有糖肽的囊泡中添加麦胚凝集素（WGA）后，观察到膜内糖肽的囊泡内交联和囊泡聚集。在相变温度以上，GlcNAc可拮抗囊泡内交联。然而，聚集的解离需要添加更强的拮抗剂N,N'-二乙酰壳二糖。在相变温度以上向DPPC囊泡中添加糖肽会降低膜流动性。然而，随后添加WGA会导致脂质双层膜表面或疏水核心处的膜流动性大幅增加。利用两种具有不同效力的拮抗剂，这种膜流动性的增加归因于两个因素：一是WGA介导的膜内糖肽交联，另一个是聚集时囊泡的紧密接触。
