STRUCTURAL STUDIES OF FARNESYLATED RAS ASSOCIATED W/ MEMBRANE BILAYERS

M. sexta apolipophorin-III是一个166残基可交换的 昆虫天蛾的载脂蛋白参与脂质 在循环系统中的运输过程。 这是一个 脂质相关蛋白，但它不是跨膜蛋白。 在其水溶性形式中，这种蛋白质已经结晶， 发现结构采用五螺旋束构象。 脂质 缔合被认为涉及剧烈的构象变化 其中螺旋束解开。 由此产生的脂蛋白颗粒 被认为是一个球形的形状，外核是蛋白质 包围着疏水脂质的内核。 蛋白质 推测具有直接朝向 水环境，其疏水区域朝向脂质 核心 固态NMR谱记录的均匀15 N 在玻璃板上的脂质双层中标记的载脂蛋白- III。 的 得到的15 N化学位移谱表明， 在整个15 N粉末图案范围内的强度， 强度在？与典型粉末相比， 模式分布 这一结果表明， 蛋白质以螺旋轴取向，螺旋轴沿着排列在双层上 正常

M. sexta apolipophorin-III is a 166 residue exchangeable apolipoprotein from the insect Manduca Sexta involved in the lipid transport processes within the circulatory system. It is a lipid-associated protein, however it is not a transmembrane protein. In its water-soluble form, this protein has been crystallized, and the structure was found to adopt a five-helix bundle conformation. Lipid association is believed to involve a drastic conformational change wherein the helix bundle unravels. The resulting lipoprotein particle is believed to adopt a sphere-like shape with an outer core of protein surrounding an inner core of hydrophobic lipid. The protein presumably orients with hydrophylic regions directed towards the aqueous environment, and its hydrophobic regions toward the lipid core. Solid-state NMR spectra were recorded of the uniformly 15N labeled apolipophorin - III in lipid bilayers on glass plates. The resulting 15N chemical shift spectrum indicated a dispersion of intensities across the 15N powder pattern range with an increase of intensity at the ?33 discontinuity compared to the typical powder pattern distribution. This result indicates a portion of the sites in the protein orient with a helical axis aligned along the bilayer normal.