Investigating the interaction of saposin c with POPS and POPC phospholipids: A solid-state NMR spectroscopic study
Investigating the interaction of saposin c with POPS and POPC phospholipids: A solid-state NMR spectroscopic study
复制标题
DOI：
10.1529/biophysj.107.107789
复制
发表时间：
2007-11-01
影响因子：
3.4
通讯作者：
Lorigan, Gary A.
中科院分区：
文献类型：
--
作者：
Abu-Baker, Shadi;Qi, Xiaoyang;Lorigan, Gary A.
鞘脂激活蛋白C（SapC）与带负电荷的磷脂如磷脂酰丝氨酸（PS）的相互作用对其生物学功能是必不可少的。在这项研究中，将Sap C（最初在弱酸中质子化）插入由1-棕榈酰-2-油酰-sn-甘油-3-[磷酸-L-丝氨酸]（带负电荷，POPS）或1-棕榈酰-2-油酰-sn-甘油-3-磷酸胆碱（带中性电荷，POPC）组成的多层囊泡（MLV）中。然后使用固态NMR光谱在中性pH（7.0）条件下研究MLV。使用POPC-d（31）或POPS-d（31）酰基链的2 H序参量曲线以及磷脂头部基团的P-31化学位移各向异性宽度和P-31 T-1弛豫时间，比较Sap C-POPS和Sap C-POPC MLV（在相同条件下制备）的2 H和P-31固态NMR光谱数据。所有这些固态NMR光谱方法表明，质子化的SAP C干扰的POPS双层，而不是POPC脂质双层。这些观察结果表明，质子化的SAP C插入PS双层，并形成一个稳定的复合物，即使在中性缓冲液条件下重悬后的脂质。此外，P-31固体核磁共振光谱研究的机械取向的磷脂在玻璃板上进行和扰动的Sap C的POPS和POPC双层的影响进行了比较。与POPC双层不同，数据表明质子化的Sap C（最初在弱酸中质子化）无法在中性pH下在玻璃板上产生良好取向的POPS双层。相反，未质子化的Sap C（最初溶解在中性缓冲液中）与POPS磷脂没有显着相互作用，使其在中性pH下产生良好取向的双层。
The interaction of Saposin C (Sap C) with negatively charged phospholipids such as phosphatidylserine (PS) is essential for its biological function. In this study, Sap C (initially protonated in a weak acid) was inserted into multilamellar vesicles (MLVs) consisting of either 1-palmitoyl-2-oleoyl-sn-glycero-3-[phospho-L-serine] (negatively charged, POPS) or 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (neutrally charged, POPC). The MLVs were then investigated using solid-state NMR spectroscopy under neutral pH (7.0) conditions. The 2 H and P-31 solid-state NMR spectroscopic data of Sap C-POPS and Sap C-POPC MLVs (prepared under the same conditions) were compared using the 2 H order parameter profiles of the POPC-d(31) or POPS-d(31) acyl chains as well as the P-31 chemical shift anisotropy width and P-31 T-1 relaxation times of the phospholipids headgroups. All those solid-state NMR spectroscopic approaches indicate that protonated Sap C disturbs the POPS bilayers and not the POPC lipid bilayers. These observations suggest for the first time that protonated Sap C inserts into PS bilayers and forms a stable complex with the lipids even after resuspension under neutral buffer conditions. Additionally, P-31 solid-state NMR spectroscopic studies of mechanically oriented phospholipids on glass plates were conducted and perturbation effect of Sap C on both POPS and POPC bilayers was compared. Unlike POPC bilayers, the data indicates that protonated Sap C (initially protonated in a weak acid) was unable to produce well-oriented POPS bilayers on glass plates at neutral pH. Conversely, unprotonated Sap C (initially dissolved in a neutral buffer) did not interact significantly with POPS phospholipids allowing them to produce well-oriented bilayers at neutral pH.