Schindler H, Rosenbusch J P
Proc Natl Acad Sci U S A. 1981 Apr;78(4):2302-6. doi: 10.1073/pnas.78.4.2302.
Planar bilayers formed from Escherichia coli outer membrane vesicles exhibit conductance properties similar to those previously observed in bilayers reconstituted from aggregates of matrix protein, the major outer membrane protein. Discrete conductance steps are observed, reflecting voltage-dependent transmembrane channels. These exist in clusters which are activated by voltage. After activation, channels close with increasing potentials and reopen reversibly at lower voltage. Depending on the sign of the potential, two distinct closed states of the pores are observed. Cooperative interactions, hysteresis effects, relaxation times, and values of channel conductance depend on cluster size. These properties provide the reference data for the reconstitution of membrane function from individual components. Planar bilayers were formed from vesicles containing either solubilized matrix protein in a homogeneous trimeric state or bacterial glycolipid (lipopolysaccharide), or both. Activation of channel conductance required the presence of glycolipid and the formation of channel clusters, leading to conductance properties of the channels closely resembling those observed in native outer membranes. At very low concentrations of trimers, irreversible association to clusters by lateral diffusion was observed. Nearly quantitative recoveries of channels allowed the assignment of three pores per trimer.
由大肠杆菌外膜囊泡形成的平面双层膜表现出的电导特性，与之前在由主要外膜蛋白——基质蛋白聚集体重构的双层膜中观察到的电导特性相似。观察到离散的电导阶跃，反映出电压依赖性跨膜通道。这些通道以簇的形式存在，且由电压激活。激活后，通道随着电位升高而关闭，并在较低电压下可逆地重新开放。根据电位的正负，可观察到孔的两种不同关闭状态。协同相互作用、滞后效应、弛豫时间和通道电导值取决于簇的大小。这些特性为从单个组件重构膜功能提供了参考数据。平面双层膜由含有均三聚体状态的可溶性基质蛋白、细菌糖脂（脂多糖）或两者的囊泡形成。通道电导的激活需要糖脂的存在以及通道簇的形成，从而导致通道的电导特性与天然外膜中观察到的非常相似。在极低浓度的三聚体下，观察到通过横向扩散与簇的不可逆缔合。通道几乎定量的恢复使得每个三聚体可分配三个孔。
