Ting-Beall H P, Tosteson M T, Gisin B F, Tosteson D C
J Gen Physiol. 1974 Apr;63(4):492-508. doi: 10.1085/jgp.63.4.492.
THIS PAPER REPORTS THE EFFECTS OF PEPTIDE PV (PRIMARY STRUCTURE: cyclo-(D-val-L-pro-L-val-D-pro)(delta)) on the electrical properties of sheep red cell lipid bilayers. The membrane conductance (G(m)) induced by PV in either Na(+) or K(+) medium is proportional to the concentration of PV in the aqueous phase. The PV concentration required to produce a comparable increase in G(m) in K(+) medium is about 10(4) times greater than for its analogue, valinomycin (val). Although the selectivity sequence for PV and val is similar, K(+) greater, similar Rb(+) > Cs(+) > NH(4) (+) > TI(+) > Na(+) > Li(+); the ratio of GGm in K(+) to that in Na(+) is about 10 for PV compared to > 10(3) for val. When equal concentrations of PV are added to both sides of a bilayer, the membrane current approaches a maximum value independent of voltage when the membrane potential exceeds 100 mV. When PV is added to only one side of a bilayer separating identical salt solutions of either Na(+) or K(+) salts, rectification occurs such that the positive current flows more easily away rather than toward the side containing the carrier. Under these conditions, a large, stable, zero-current potential (VVm) is also observed, with the side containing PV being negative. The magnitude of this VVm is about 90 mV and relatively independent of PV concentration when the latter is larger than 2 Times; 10(-5) M. From a model which assumes that V(m) equals the equilibrium potential for the PV-cation complexes (MS(+)) and that the reaction between PV and cations is at equilibrium on the two membrane surfaces, we compute the permeability of the membrane to free PV to be about 10(-5) cm s(-1), which is about 10(-7) times the permeability of similar membranes to free val. This interpretation is supported by the fact that the observed values of V(m) are in agreement with the calculated equilibrium potential for MS(+) over a wide range of ratios of concentrations of total PV in the two bathing solutions, if the unstirred layers are taken into account in computing the MS(+) concentrations at the membrane surfaces.
本文报道了肽PV（一级结构：环（D-缬氨酸-L-脯氨酸-L-缬氨酸-D-脯氨酸）（δ））对绵羊红细胞脂质双层膜电性质的影响。在Na(+)或K(+)介质中，PV诱导的膜电导（G(m)）与水相中PV的浓度成正比。在K(+)介质中产生与缬氨霉素（val）类似的G(m)增加所需的PV浓度约比其类似物大10(4)倍。尽管PV和val的选择性顺序相似，即K(+)＞Rb(+)＞Cs(+)＞NH(4) (+)＞TI(+)＞Na(+)＞Li(+)；但PV在K(+)介质中的G(m)与在Na(+)介质中的G(m)之比约为10，而val的该比值＞10(3)。当向双层膜两侧加入等浓度的PV时，当膜电位超过100 mV时，膜电流接近一个与电压无关的最大值。当将PV仅添加到分隔相同Na(+)或K(+)盐溶液的双层膜的一侧时，会发生整流现象，使得正电流更容易流向远离而非朝向含有载体的一侧。在这些条件下，还观察到一个大的、稳定的零电流电位（VVm），含有PV的一侧为负。当PV浓度大于2×10(-5) M时，该VVm的大小约为90 mV，且相对独立于PV浓度。根据一个模型，该模型假设V(m)等于PV - 阳离子复合物（MS(+)）的平衡电位，且PV与阳离子之间的反应在两个膜表面处于平衡，我们计算出膜对游离PV的渗透率约为10(-5) cm s(-1)，这约为类似膜对游离val渗透率的10(-7)倍。如果在计算膜表面的MS(+)浓度时考虑到未搅拌层，则在两种浴液中总PV浓度的广泛比例范围内，观察到的V(m)值与计算出的MS(+)平衡电位一致，这一事实支持了这种解释。
