Reinl H M, Bayerl T M
Technische Universität München, Physik Department E22, Garching, Germany.
Biochim Biophys Acta. 1993 Sep 19;1151(2):127-36. doi: 10.1016/0005-2736(93)90095-h.
The interaction of myelin basic protein (MBP) with single bilayers on a solid support (planar and spherical support) is studied by deuterium nuclear magnetic resonance (2H-NMR), differential scanning calorimetry (DSC) and polarized attenuated total reflection infrared spectroscopy (ATR-IR). The single bilayer consisted of either DMPC or of a binary mixture of DMPC with 10-20 mol% of an acidic phospholipid (DMPG, DMPS or DMPA). All methods applied indicate that MBP strongly interacts with the binary lipid systems but not with the pure DMPC bilayers. The interaction is predominantly electrostatic in nature and does not depend on the choice of a particular acidic lipid (for the binary systems). In particular, the results give no indication for a hydrophobic interaction of MBP with the membrane. Our data provide evidence that, in contrast to previous findings, no demixing and/or domain formation in the binary systems is induced due to the MBP coupling. The infrared order parameter was determined for both lipid components of the binary systems and shows a remarkable change for both lipids due to the interaction with MBP while the NMR order parameter remained essentially unchanged. This is discussed in terms of the different timescales characteristic for both methods. The single supported bilayer responds to the MBP coupling as a whole although only 50% of the bilayer surface is accessible to the protein, indicating a strong coupling between the two bilayer leaflets via the hydrophobic chain region. Moreover, the asymmetric coupling of MBP to the single supported bilayer does not result in a significant redistribution of lipids between the two bilayer leaflets. NMR relaxation time measurements in the headgroup and chain region of DMPG and DMPC suggest that the lateral diffusion coefficient of the acidic lipid decreases significantly due to the coupling with MBP while the zwitterionic DMPC is not affected.
通过氘核磁共振（2H-NMR）、差示扫描量热法（DSC）和偏振衰减全反射红外光谱法（ATR-IR）研究了髓鞘碱性蛋白（MBP）与固体支持物（平面和球形支持物）上的单层双分子层之间的相互作用。单层双分子层由二肉豆蔻酰磷脂酰胆碱（DMPC）或DMPC与10 - 20 mol%酸性磷脂（二肉豆蔻酰磷脂酰甘油（DMPG）、二肉豆蔻酰磷脂酰丝氨酸（DMPS）或二肉豆蔻酰磷脂酸（DMPA））的二元混合物组成。所应用的所有方法均表明，MBP与二元脂质体系强烈相互作用，但与纯DMPC双分子层不相互作用。这种相互作用本质上主要是静电作用，并且不依赖于特定酸性脂质（对于二元体系）的选择。特别地，结果未显示MBP与膜之间存在疏水相互作用。我们的数据提供了证据，与先前的发现相反，由于MBP的耦合，二元体系中不会诱导相分离和/或结构域形成。测定了二元体系中两种脂质成分的红外序参数，由于与MBP相互作用，两种脂质的红外序参数均有显著变化，而NMR序参数基本保持不变。根据两种方法各自特有的不同时间尺度对此进行了讨论。尽管只有50%的双分子层表面可被蛋白质接触，但单个支持的双分子层作为一个整体对MBP耦合作出响应，这表明两个双分子层小叶通过疏水链区域存在强耦合。此外，MBP与单个支持双分子层的不对称耦合不会导致脂质在两个双分子层小叶之间发生显著重新分布。对DMPG和DMPC的头部基团和链区域进行的NMR弛豫时间测量表明，由于与MBP耦合，酸性脂质的横向扩散系数显著降低，而两性离子DMPC不受影响。
