Probing sugar translocation through maltoporin at the single channel level
Probing sugar translocation through maltoporin at the single channel level
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DOI：
10.1016/s0014-5793(00)01753-1
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发表时间：
2000-07-07
期刊：
影响因子：
3.5
通讯作者：
Winterhalter, M
中科院分区：
文献类型：
--
作者：
Bezrukov, SM;Kullman, L;Winterhalter, M
在单通道水平上研究了糖通过大肠杆菌麦芽糖蛋白的渗透，麦芽糖蛋白是一种促进麦芽糖糊精在细菌外膜转运的三聚体蛋白。对于大糖，如麦芽糖己糖，单个糖分子渗透到通道中的基本事件是很容易观察到的。在低糖浓度下，无糖溶液中麦芽糖嘌呤通道关闭的基本事件是其初始电导的三分之一。统计肛门吗?在较高糖浓度下，这种闭合表明麦芽糖嘌呤通道的所有三个孔都独立地运输糖。有趣的是，虽然通道电导只有轻微的不对称，在-200 mV时的值比+200 mV时高10%左右（从蛋白质添加的角度来看），但糖结合常数对电压极性的依赖性的不对称性约为20倍。结合我们的数据和对噬菌体-h的观察，我们得出结论，糖的停留时间对来自细菌膜胞内侧的负电压更敏感（并减少）。(C) 2000年欧洲生化学会联合会。Elsevier Science B.V.版权所有。
Sugar permeation through maltoporin of Escherichia coli, a trimer protein that facilitates maltodextrin translocation across outer bacterial membranes, was investigated at the single channel level. For large sugars, such as maltohexaose, elementary events of individual sugar molecule penetration into the channel a ere readily observed. At small sugar concentrations an elementary event consists of maltoporin channel closure by one third of its initial conductance in sugar-free solution. Statistical anal? sis of such closures at higher sugar concentrations shows that all three pores of the maltoporin channel transport sugars independently. interestingly, while channel conductance is only slightly asymmetric showing about 10% higher values at -200 mV than at +200 mV (from the side of protein addition), asymmetry in dependence of the sugar binding constant on the voltage polarity is about 20 times higher. Combining our data with observations made with bacteriophage-h we conclude that the sugar residence time is much more sensitive to (and is decreased by) voltages that are negative from the intra-cell side of the bacterial membrane. (C) 2000 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.