Effect of hydrophobic surfactant proteins SP-B and SP-C on phospholipid monolayers. Protein structure studied using 2D IR and beta correlation analysis.
Effect of hydrophobic surfactant proteins SP-B and SP-C on phospholipid monolayers. Protein structure studied using 2D IR and beta correlation analysis.
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DOI：
10.1016/s0006-3495(02)73973-8
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发表时间：
2002-10
影响因子：
3.4
通讯作者：
S. Shanmukh;P. Howell;J. Baatz;R. Dluhy
中科院分区：
文献类型：
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作者：
S. Shanmukh;P. Howell;J. Baatz;R. Dluhy
我们应用二维红外（2D IR）和βν相关光谱对空气-水界面处脂质-蛋白质单层中的肺表面活性蛋白SP-B和SP-C进行了原位红外光谱研究。对于SP-B和SP-C，统计窗口自相关方法确定了两个单独的表面压力区域，其中包含最大酰胺I强度变化：4-25 mN/m和25-40 mN/m。对SP-C的二维红外光谱和βν相关分析表明，SP-C具有多种二级结构构象，包括α-螺旋、β-折叠和β-折叠结构的分子间聚集。主α-螺旋带在高表面压力下分裂成两个峰，表明两种不同的螺旋构象。在低表面压力下，所有构象的SP-C分子反应相同，增加表面压力和重新取向的相位与对方。高于25 mN/m，然而，增加的表面压力选择性地影响共存的蛋白质构象，导致蛋白质构象的独立重定向。SP-B的异步2D IR光谱显示存在两个α-螺旋组分，与SP-B中两个独立的α-螺旋群体一致-与脂质链相关的疏水部分和平行于膜表面的亲水部分。两个α-螺旋交叉峰之间的相关强度分布表明，在低表面压下，更疏水的螺旋部分占主导地位，而在高表面压下，更亲水的螺旋部分占主导地位。不同的SP-B二级结构反应相同，增加表面压力，导致所有SP-B亚基的重新取向，彼此同相。
We have applied two-dimensional infrared (2D IR) andβνcorrelation spectroscopy to in-situ IR spectroscopy of pulmonary surfactant proteins SP-B and SP-C in lipid–protein monolayers at the air—water interface. For both SP-B and SP-C, a statistical windowed autocorrelation method identified two separate surface pressure regions that contained maximum amide I intensity changes: 4–25 mN/m and 25–40 mN/m. For SP-C, 2D IR andβνcorrelation analyses of these regions indicated that SP-C adopts a variety of secondary structure conformations, includingα-helix,β-sheet, and an intermolecular aggregation of extendedβ-sheet structure. The mainα-helix band split into two peaks at high surface pressures, indicative of two different helix conformations. At low surface pressures, all conformations of the SP-C molecule reacted identically to increasing surface pressure and reoriented in phase with each other. Above 25 mN/m, however, the increasing surface pressure selectively affected the coexisting protein conformations, leading to an independent reorientation of the protein conformations. The asynchronous 2D IR spectrum of SP-B showed the presence of twoα-helix components, consistent with two separate populations ofα-helix in SP-B—a hydrophobic fraction associated with the lipid chains and a hydrophilic fraction parallel to the membrane surface. The distribution of correlation intensity between the twoα-helix cross peaks indicated that the more hydrophobic helix fraction predominates at low surface pressures whereas the more hydrophilic helix fraction predominates at high surface pressures. The different SP-B secondary structures reacted identically to increasing surface pressure, leading to a reorientation of all SP-B subunits in phase with one another.