Anosov Andrey, Borisova Elizaveta, Smirnova Elena, Korepanova Eugenia, Osipov Anatoly
The Department of Medical and Biological Physics, Sechenov First Moscow State Medical University (Sechenov University), 119991 Moscow, Russia.
Kotelnikov Institute of Radioengineering and Electronics of RAS, 125009 Moscow, Russia.
Membranes (Basel). 2023 Feb 24;13(3):268. doi: 10.3390/membranes13030268.
The study of the electrical parameters of asolectin bilayer lipid membranes in the presence of cytochrome c (cyt c) at various concentrations showed that an increase in the concentration of cyt c leads to an increase in the membrane conductance and the appearance of through pores. The studied membranes did not contain cardiolipin, which is commonly used in studying the effect of cyt c on membrane permeability. In the presence of cyt c, discrete current fluctuations were recorded. The occurrence of these fluctuations may be associated with the formation of through pores. The diameter of these pores was 0.8 nm, which is smaller than the size of the cyt c globule (3 nm). Measurements carried out at pH values from 6.4 to 8.4 showed that the concentration dependence of the membrane conductance increases with increasing pH. To assess the binding of cyt c to the bilayer, we measured the concentration and pH dependences of the difference in surface potentials induced by the unilateral addition of cyt c. The amount of bound cyt c at the same concentrations decreased with increasing pH, which did not correspond to the conductance trend. An analysis of conductance traces leads to the conclusion that an increase in the integral conductance of membranes is associated with an increase in the lifetime of pores. The formation of "long-lived" pores, of which the residence time in the open state is longer than in the closed state, was achieved at various combinations of pHs and cyt c concentrations: the higher the pH, the lower the concentration at which the long-lived pores appeared and, accordingly, a higher conductance was observed. The increase in conductance and the formation of transmembrane pores are not due to the electrostatic interaction between cyt c and the membrane. We hypothesize that an increase in pH leads to a weakening of hydrogen bonds between lipid heads, which allows cyt c molecules to penetrate into the membrane. This disrupts the order of the bilayer and leads to the occurrence of through pores.
对不同浓度细胞色素c（cyt c）存在下大豆卵磷脂双层脂质膜电参数的研究表明，cyt c浓度的增加会导致膜电导增加以及出现贯通孔。所研究的膜不含心磷脂，而心磷脂常用于研究cyt c对膜通透性的影响。在cyt c存在的情况下，记录到了离散的电流波动。这些波动的出现可能与贯通孔的形成有关。这些孔的直径约为0.8纳米，小于cyt c球蛋白的尺寸（约3纳米）。在pH值从6.4到8.4范围内进行的测量表明，膜电导的浓度依赖性随pH值升高而增加。为了评估cyt c与双层膜的结合，我们测量了单侧添加cyt c所诱导的表面电位差的浓度和pH依赖性。相同浓度下结合的cyt c量随pH值升高而减少，这与电导趋势不相符。对电导曲线的分析得出结论，膜积分电导的增加与孔寿命的增加有关。在不同的pH值和cyt c浓度组合下实现了“长寿命”孔的形成，其中开放状态下的停留时间比关闭状态下长：pH值越高，出现长寿命孔的浓度越低，相应地观察到的电导越高。电导的增加和跨膜孔的形成并非由于cyt c与膜之间的静电相互作用。我们推测，pH值升高会导致脂质头部之间氢键减弱，这使得cyt c分子能够渗透到膜中。这破坏了双层膜的有序性并导致贯通孔的出现。
