Nabet A, Boggs J M, Pézolet M
Département de Chimie, Université Laval, Québec, Canada.
Biochemistry. 1994 Dec 13;33(49):14792-9. doi: 10.1021/bi00253a018.
The effect of bovine myelin basic protein (MBP) on dimyristoylphosphatidic acid (DMPA) and phosphatidic acid prepared from egg yolk phosphatidylcholine (EPA) has been investigated by transmission and attenuated total reflectance (ATR) Fourier transform infrared spectroscopy. Interaction of MBP with DMPA and EPA dispersions decreases the lipid acyl chain conformational disorder as a consequence of hydrophobic interactions of the protein with the lipids. Since these effects are more important for EPA dispersions than for DMPA, MBP is believed to penetrate more into EPA bilayers. This could be due to the fact that the hydrogen bond network formed by the charged polar headgroups of EPA is weaker than that of DMPA. This is supported by the spectra of the phosphate region showing that the phosphate groups of EPA are less hydrogen bonded than DMPA. In the presence of MBP, the hydrogen bond network is replaced by electrostatic interactions of the protein with the polar headgroups of the lipid. Infrared spectra of the polar headgroup region also show evidence that MBP enhanced the second ionization state of the phosphate group at neutral pH, this effect being more important for EPA than for DMPA bilayers. Also, infrared spectra of the lipid carbonyl stretching region show evidence that MBP limits the accessibility of water molecules to the interfacial part of the lipid bilayer. Finally, ATR measurements on oriented films of lipid/protein complexes indicate that the penetration of the protein into the lipid bilayer is followed by a reorientation of the lipid acyl chains toward the normal to the bilayer in the case of EPA.(ABSTRACT TRUNCATED AT 250 WORDS)
通过透射和衰减全反射（ATR）傅里叶变换红外光谱法，研究了牛髓鞘碱性蛋白（MBP）对由蛋黄磷脂酰胆碱（EPA）制备的二肉豆蔻酰磷脂酸（DMPA）和磷脂酸的影响。MBP与DMPA和EPA分散体的相互作用降低了脂质酰基链的构象无序性，这是蛋白质与脂质疏水相互作用的结果。由于这些效应在EPA分散体中比在DMPA中更显著，因此认为MBP能更多地穿透到EPA双层中。这可能是因为EPA带电极性头基团形成的氢键网络比DMPA的弱。磷酸盐区域的光谱支持了这一点，表明EPA的磷酸基团形成的氢键比DMPA少。在MBP存在下，氢键网络被蛋白质与脂质极性头基团的静电相互作用所取代。极性头基团区域的红外光谱也表明，MBP在中性pH下增强了磷酸基团的第二电离态，这种效应在EPA双层中比在DMPA双层中更显著。此外，脂质羰基伸缩区域的红外光谱表明，MBP限制了水分子接近脂质双层的界面部分。最后，对脂质/蛋白质复合物取向膜的ATR测量表明，在EPA的情况下，蛋白质穿透脂质双层后，脂质酰基链会重新取向至垂直于双层的方向。（摘要截选至250字）
