Tosteson M T, Tosteson D C, Rubnitz J
Acta Physiol Scand Suppl. 1980;481:21-5.
The purpose of the experiments described in this paper was to assess the binding of cholera toxin to bilayers containing its receptor, the monosialoganglioside, GMl. The assay was based on the fact that GMl confers on the bilayer a negative surface charge. The magnitude of this surface charge was estimated by measuring the electrical conductance (G) of the bilayers exposed to nonactin-K+ under conditions where G is directly proportional to the potassium concentration in the aqueous solutions immediatey adjacent to the membrane surface. When bilayers were formed from mixtures of GMl and glycerolmonooleate (GMO), it was found that the molar ratio of the lipids in the bilayer was the same as that in the membrane forming solution. It was further found that cholera toxin or the binding subunit of the toxin (choleragenoid) bind to GMO bilayers containing GMl (but not to GMO bilayers containing phosphatidyl serine or disialoganglioside GDla). The value of the apparent dissociation constant for the binding of choleragen to its receptor was found to be 10(-11) M, comparable to values found in intact cells.
本文所述实验的目的是评估霍乱毒素与含有其受体单唾液酸神经节苷脂GM1的双层膜的结合情况。该测定基于GM1赋予双层膜负表面电荷这一事实。通过在电导率（G）与紧邻膜表面的水溶液中钾浓度成正比的条件下，测量暴露于缬氨霉素 - K⁺的双层膜的电导（G）来估算该表面电荷的大小。当由GM1和甘油单油酸酯（GMO）的混合物形成双层膜时，发现双层膜中脂质的摩尔比与形成膜的溶液中的相同。进一步发现霍乱毒素或毒素的结合亚基（类霍乱毒素）与含有GM1的GMO双层膜结合（但不与含有磷脂酰丝氨酸或二唾液酸神经节苷脂GDla的GMO双层膜结合）。发现霍乱原与其受体结合的表观解离常数的值为10⁻¹¹ M，与在完整细胞中发现的值相当。
