Lüneberg J, Martin I, Nüssler F, Ruysschaert J M, Herrmann A
Mathematisch Naturwissenschaftliche Fakultät I, Institut für Biologie/Biophysik, Humboldt Universität, Berlin, Federal Republic of Germany.
J Biol Chem. 1995 Nov 17;270(46):27606-14. doi: 10.1074/jbc.270.46.27606.
The secondary structure of a 20-amino acid length synthetic peptide corresponding to the N terminus of the second subunit of hemagglutinin (HA2) of influenza virus A/PR8/34 and its interaction with phospholipid bilayers are investigated using ESR, Fourier transform infrared (FTIR), and CD spectroscopy. N-terminal spin labeling of the peptide did not affect the secondary structure of the peptide either in solution or when bound to liposomes as revealed by FTIR and CD spectroscopy. ESR spectra show that the mobility of the labeled peptide is dramatically restricted in the presence of phosphatidylcholine liposomes, suggesting a strong binding to the lipid membranes. The N terminus of the peptide penetrates into the membrane and is located within the hydrophobic core. We find an oblique insertion of the peptide into the lipid bilayer with an angle of about 45 degrees between helix axis and membrane plane using FTIR spectroscopy. No gross changes of the peptide's orientation, motion, and secondary structure were observed between pH 7.4 and pH 5.0. A model of the insertion of the fusion sequence of HA2 into a lipid bilayer is presented taking into account recent investigations on the low pH conformation of HA2 (Bullough, P. A., Hughson, F. M., Skehel, J. J., and Wiley, D. C. (1994) Nature 371, 37-43).
利用电子顺磁共振（ESR）、傅里叶变换红外光谱（FTIR）和圆二色光谱（CD），研究了与甲型流感病毒A/PR8/34血凝素（HA）第二亚基N端对应的20个氨基酸长度合成肽的二级结构及其与磷脂双层的相互作用。FTIR和CD光谱显示，肽的N端自旋标记在溶液中或与脂质体结合时均不影响肽的二级结构。ESR光谱表明，在磷脂酰胆碱脂质体存在下，标记肽的流动性显著受限，表明其与脂质膜有强烈结合。肽的N端穿透膜并位于疏水核心内。利用FTIR光谱，我们发现肽以约45度的角度倾斜插入脂质双层，螺旋轴与膜平面之间呈该角度。在pH 7.4和pH 5.0之间，未观察到肽的取向、运动和二级结构有明显变化。结合最近对HA2低pH构象的研究（Bullough, P. A., Hughson, F. M., Skehel, J. J., and Wiley, D. C. (1994) Nature 371, 37 - 43），提出了HA2融合序列插入脂质双层的模型。
