Department of Physics, Laboratory of Molecular Biophysics and Medical Physics, Alexandru I. Cuza University, Iasi, Romania.
PLoS One. 2011;6(9):e25276. doi: 10.1371/journal.pone.0025276. Epub 2011 Sep 27.
While it is accepted that biomembrane asymmetry is generated by proteins and phospholipids distribution, little is known about how electric changes manifested in a monolayer influence functional properties of proteins localized on the opposite leaflet. Herein we used single-molecule electrophysiology and investigated how asymmetric changes in the electrostatics of an artificial lipid membrane monolayer, generated oppositely from where alamethicin--a model voltage-gated ion channel--was added, altered peptide activity. We found that phlorizin, a membrane dipole potential lowering amphiphile, augmented alamethicin activity and transport features, whereas the opposite occurred with RH-421, which enhances the monolayer dipole potential. Further, the monolayer surface potential was decreased via adsorption of sodium dodecyl sulfate, and demonstrated that vectorial modification of it also affected the alamethicin activity in a predictive manner. A new paradigm is suggested according to which asymmetric changes in the monolayer dipole and surface potential extend their effects spatially by altering the intramembrane potential, whose gradient is sensed by distantly located peptides.
虽然人们普遍认为生物膜的不对称性是由蛋白质和磷脂的分布产生的，但对于电变化如何影响位于相对叶面上的蛋白质的功能特性，人们知之甚少。在此，我们使用单分子电生理学研究了人工脂质膜单层的静电不对称变化如何改变局部定位的肽的活性。我们发现，紫堇素，一种降低膜偶极子势的两亲分子，增强了alamethicin 的活性和转运特性，而相反的情况则发生在 RH-421 上，它增强了单层偶极子势。此外，通过十二烷基硫酸钠的吸附降低了单层表面电势，并证明其矢量修饰也以可预测的方式影响 alamethicin 的活性。根据这一观点，单层偶极子和表面电势的不对称变化通过改变跨膜电势来扩展其空间效应，而跨膜电势的梯度则由远距离定位的肽来感知。
