Vernoux Nathalie, Maniti Ofelia, Marcillat Olivier, Vial Christian, Granjon Thierry
Université de Lyon, France.
Biochimie. 2009 Jun;91(6):752-64. doi: 10.1016/j.biochi.2009.03.014. Epub 2009 Mar 31.
Our study highlights the tight relationship between protein binding to monolayers and the phase-state of the phospholipids. Interaction of mitochondrial creatine kinase with phospholipidic membranes was analysed using a two-phase monolayer system containing anionic phospholipids under chain mismatch conditions. Monolayers were made up of mixtures of DMPC/DPPG or DPPC/DMPG containing 40% negatively charged phospholipids which is approximately the negative charge content of the mitochondrial inner membrane. Langmuir isotherms of these monolayers showed that they underwent a phase transition from a liquid expanded state to a liquid-condensed phase at about 2 mN/m and 5 mN/m respectively. Interface morphology modifications caused by injection of mtCK under these monolayers at low or high surface pressure were monitored by Brewster angle microscopy. This work provides evidence that the presence at the air/water interface of discrete domains with increased charge density, may lead to difference in partition of soluble proteins such as mtCK, interacting with the lipid monolayer. Conversely these proteins may help to organize charged phospholipid domains in a membrane.
我们的研究突出了蛋白质与单层膜结合和磷脂相态之间的紧密关系。在线粒体肌酸激酶与磷脂膜相互作用的研究中,我们使用了一种包含阴离子磷脂的两相单层系统,该系统处于链错配条件下。单层膜由含有40%带负电荷磷脂的DMPC/DPPG或DPPC/DMPG混合物组成,这大约是线粒体内膜的负电荷含量。这些单层膜的朗缪尔等温线表明,它们分别在约2 mN/m和5 mN/m时从液体扩张态转变为液体凝聚态。通过布鲁斯特角显微镜监测在低表面压力或高表面压力下向这些单层膜注射线粒体肌酸激酶所引起的界面形态变化。这项工作提供了证据,即空气/水界面处电荷密度增加的离散区域的存在,可能导致与脂质单层相互作用的可溶性蛋白质(如线粒体肌酸激酶)分配的差异。相反,这些蛋白质可能有助于在膜中组织带电荷的磷脂区域。