Hydrophobic mismatch in gramicidin A'/lecithin systems.
Hydrophobic mismatch in gramicidin A'/lecithin systems.
复制标题
短杆菌肽 A/卵磷脂系统中的疏水错配。
作者：
Watnick,PI;Chan,SI;Dea,P
化学和生物化学系，加州州立大学洛杉矶分校，洛杉矶，加州90032 1989年10月10日接收; 1990年3月29日接收的修订版摘要：短杆菌肽A '（GA'）已被添加到三种不同疏水厚度的脂质系统中：二肉豆蔻酰甘油（DML）、二棕榈酰甘油（DPL）和二硬脂酰甘油（DSL）。用~（31）P和~ 2 H NMR研究了GA ′的疏水部分与脂双层烃链长度的相似性。已发现疏水性错配在DML双层系统中是最严重的，而在DSL的情况下是最小的。此外，通过~ 2 H NMR弛豫测量，得到了疏水失配对双层膜协同性能的影响。结果表明，将肽掺入双层破坏了纯多层脂质分散体的协同指向矢波动特性。最后，已知的从双层到反六方（Hu）相的转变发生时的GA '/卵磷脂比率（货车Echteld等人，1982年; Chupín等人，1987）显示依赖于磷脂的酰基链长度。提出了这种链长依赖性的理由。（jramicidin A ′（GA ′）是由短芽孢杆菌细菌产生的三种相关线性十五肽的混合物。通过与RNA聚合酶结合，GA'被认为抑制参与营养生长的基因的转录（Fisher和布卢门塔尔，1982）。在脂质双层中，GA'形成允许单价阳离子通过的跨膜通道。虽然这种功能在体内似乎并不重要，但在研究膜通道、膜/蛋白质相互作用和跨膜螺旋时，使用GA'作为一种简单模型的可能性已经激发了人们对其膜结合构象的兴趣。有证据表明，GA'在许多两亲性体系中作为单个螺旋二聚体存在（Urry等人，1971年，1983年）。在DML中同位素标记的GA'的NMR研究已经表明，大多数C-末端暴露于双层的亲水区域，而N-末端埋在烃区域中（Weinstein等人，1979年，1980年）。这表明GA'单体残基的N-末端位于双层的疏水区，并且可能是二聚体形成中的连接点。双层膜中GA'的二级结构的红外和拉曼光谱研究表明了β-片层氢键模式（Iqbal& Weidekamm，1980; Naik & Krimm，1984，1986）。GA ′/DML双层的更近期的固态NMR研究揭示了多重标记的GA ′中的13 C-13 C偶极偶联，其与螺距为6.3的单链螺旋一致（Cornell等人，1988年a）。建模研究表明，该β-螺旋为26-30 μ m长，内径为4 μ m（Veatch等人，1974年）。因为GA的几个色氨酸残基位于加州理工学院化学与化学工程系贡献号8343的头基附近。这项工作得到了美国公共卫生署国家普通医学科学研究院的赠款GM-22432（SIC）、GM-36132（PD）和RR-08101（PD）以及美国化学学会管理的石油研究基金的捐助者的支持。PIW获得了美国国立普通医学科学研究院颁发的国家研究服务奖（T32 GM 07616）。通信地址。
Department of Chemistry and Biochemistry, California State University at Los Angeles, Los Angeles, California 90032 Received October 10, 1989; Revised Manuscript Received March 29, 1990 abstract: Gramicidin A'(GA') has been added to three lipid systems of varying hydrophobic thicknesses: dimyristoyllecithin (DML), dipalmitoyllecithin (DPL), and distearoyllecithin (DSL). The similarity in length between the hydrophobicportion ofGA'and the hydrocarbon chains of the lipid bilayers has been studied by using 31P and 2H NMR. Hydrophobic mismatch has been found to be most severe in the DML bilayer system and minimal in the case of DSL. In addition, the effects of hydrophobic mismatch on the cooperative properties of the bilayer havebeen obtained from 2H NMR relaxation measurements. The results indicate that incorporation of the peptide into the bilayer disrupts the cooperative director fluctuations characteristic of pure multilamellar lipid dispersions. Finally, the GA'/lecithin ratio at which the well-known transformation from bilayer to reverse hexagonal (Hu) phase occurs (Van Echteld et al., 1982; Chupín et al., 1987) is shown to depend on the acyl chain length of the phospholipid. A rationale is proposed for this chain length dependence.(jramicidin A'(GA') is a mixture of three related linear pentadecapeptides produced by the Bacillus brevis bacterium. By binding to RNA polymerase, GA'is believed to inhibit the transcription of genes involved in vegetative growth (Fisher & Blumenthal, 1982). In lipid bilayers, GA'forms a transmembrane channel which allows the passage of monovalent cations. Although this function does notappear to be important in vivo, the possibility of using GA'as a simple model in the study of membrane channels, membrane/protein interactions, and transmembrane-helices has spurred much interest in its membrane-bound conformation. Evidence indicates that GA'exists as a single helical dimer in many amphipathic systems (Urry et al., 1971, 1983). NMR studies of isotopically labeled GA'in DML have shown that most of the C-terminal ends are exposed to the hydrophilic region of the bilayer, while the N-terminal ends are buried in the hydrocarbon region (Weinstein et al., 1979, 1980). This indicates that the N-terminus of the GA'monomer residues in the hydrophobic region of the bilayer and is probably the point of attachment in dimer formation. Infrared and Raman spectroscopic investigations of the secondary structure of GA'in bilayer membranes indicate a/3-sheet hydrogen-bonding pattern (Iqbal& Weidekamm, 1980; Naik & Krimm, 1984, 1986). More recent solid-state NMR studies of GA'/DML bilayers revealed 13C-13C dipolar couplings in multiply labeled GA'that are consistent with a single-stranded helix of pitch 6.3 (Cornell et al., 1988a). Modeling studies have shown this/3-helix to be 26-30 Á long with an inner diameter of 4 Á (Veatch et al., 1974). Because several of GA'’s Trp residues are located near the headgroup f Contribution No. 8343 of the Division of Chemistry and Chemical Engineering, California Institute of Technology. This work was supported by Grants GM-22432 (SIC), GM-36132 (PD), and RR-08101 (PD) from the National Institutes of General Medical Sciences, US Public Health Service, and by the donors of the Petroleum Research Fund, administered by the American Chemical Society. PIW was a recipient of a National Research Service Award (T32 GM07616) from the National Institutes of General Medical Sciences.* To whom correspondence should be addressed.