Marassi F M, Opella S J
The Wistar Institute, Philadelphia, PA 19104-4268, USA.
J Magn Reson. 2000 May;144(1):150-5. doi: 10.1006/jmre.2000.2035.
The secondary structure and topology of membrane proteins can be described by inspection of two-dimensional (1)H-(15)N dipolar coupling/(15)N chemical shift polarization inversion spin exchange at the magic angle spectra obtained from uniformly (15)N-labeled samples in oriented bilayers. The characteristic wheel-like patterns of resonances observed in these spectra reflect helical wheel projections of residues in both transmembrane and in-plane helices and hence provide direct indices of the secondary structure and topology of membrane proteins in phospholipid bilayers. We refer to these patterns as PISA (polarity index slant angle) wheels. The transmembrane helix of the M2 peptide corresponding to the pore-lining segment of the acetylcholine receptor and the membrane surface helix of the antibiotic peptide magainin are used as examples.
膜蛋白的二级结构和拓扑结构可通过检查二维（1）H -（15）N偶极耦合/（15）N化学位移极化反转自旋交换在魔角光谱来描述，该光谱来自于取向双层中均匀（15）N标记的样品。在这些光谱中观察到的特征性轮状共振模式反映了跨膜螺旋和平面内螺旋中残基的螺旋轮投影，因此提供了磷脂双层中膜蛋白二级结构和拓扑结构的直接指标。我们将这些模式称为PISA（极性指数倾斜角）轮。以对应于乙酰胆碱受体孔衬里段的M2肽的跨膜螺旋和抗菌肽蛙皮素的膜表面螺旋为例。
