Bodor Andrea, Kövér Katalin E, Mäler Lena
Laboratory of Structural Chemistry and Biology, Institute of Chemistry, Eötvös Loránd University, H-1117 Budapest, Hungary.
Department of Inorganic and Analytical Chemistry, University of Debrecen, H-4032 Debrecen, Hungary.
Biochim Biophys Acta. 2015 Mar;1848(3):760-6. doi: 10.1016/j.bbamem.2014.12.001. Epub 2014 Dec 9.
Small fast-tumbling bicelles are ideal for studies of membrane interactions at molecular level; they allow analysis of lipid properties using solution-state NMR. In the present study we used 31P NMR relaxation to obtain detailed information on lipid head-group dynamics. We explored the effect of two topologically different membrane-interacting peptides on bicelles containing either dimyristoylphosphocholine (DMPC), or a mixture of DMPC and dimyristoylphosphoglycerol (DMPG), and dihexanoylphosphocholine (DHPC). KALP21 is a model transmembrane peptide, designed to span a DMPC bilayer and dynorphin B is a membrane surface active neuropeptide. KALP21 causes significant increase in bicelle size, as evidenced by both dynamic light scattering and 31P T2 relaxation measurements. The effect of dynorphin B on bicelle size is more modest, although significant effects on T2 relaxation are observed at higher temperatures. A comparison of 31P T1 values for the lipids with and without the peptides showed that dynorphin B has a greater effect on lipid head-group dynamics than KALP21, especially at elevated temperatures. From the field-dependence of T1 relaxation data, a correlation time describing the overall lipid motion was derived. Results indicate that the positively charged dynorphin B decreases the mobility of the lipid molecules--in particular for the negatively charged DMPG--while KALP21 has a more modest influence. Our results demonstrate that while a transmembrane peptide has severe effects on overall bilayer properties, the surface bound peptide has a more dramatic effect in reducing lipid head-group mobility. These observations may be of general importance for understanding peptide-membrane interactions.
小型快速翻滚双分子层囊泡非常适合在分子水平上研究膜相互作用；它们能够利用溶液态核磁共振分析脂质特性。在本研究中，我们使用³¹P核磁共振弛豫来获取有关脂质头部基团动力学的详细信息。我们探究了两种拓扑结构不同的膜相互作用肽对含有二肉豆蔻酰磷脂酰胆碱（DMPC）、或DMPC与二肉豆蔻酰磷脂甘油（DMPG）以及二己酰磷脂酰胆碱（DHPC）混合物的双分子层囊泡的影响。KALP21是一种模型跨膜肽，设计用于跨越DMPC双层膜，强啡肽B是一种膜表面活性神经肽。动态光散射和³¹P T2弛豫测量均证明，KALP21会使双分子层囊泡尺寸显著增加。强啡肽B对双分子层囊泡尺寸的影响较为适度，不过在较高温度下可观察到对T2弛豫有显著影响。对有肽和无肽情况下脂质的³¹P T1值进行比较表明，强啡肽B对脂质头部基团动力学的影响比KALP21更大，尤其是在温度升高时。根据T1弛豫数据的场依赖性，得出了一个描述脂质整体运动的相关时间。结果表明，带正电荷的强啡肽B会降低脂质分子的流动性——特别是对于带负电荷的DMPG——而KALP21的影响则较为适度。我们的结果表明，虽然跨膜肽对整个双层膜性质有严重影响，但表面结合肽在降低脂质头部基团流动性方面具有更显著的作用。这些观察结果对于理解肽 - 膜相互作用可能具有普遍重要性。
