MECHANISM OF SUGAR-TRANSPORT THROUGH THE SUGAR-SPECIFIC LAMB CHANNEL OF ESCHERICHIA-COLI OUTER-MEMBRANE
MECHANISM OF SUGAR-TRANSPORT THROUGH THE SUGAR-SPECIFIC LAMB CHANNEL OF ESCHERICHIA-COLI OUTER-MEMBRANE
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DOI：
10.1007/bf02209137
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发表时间：
1987-01-01
影响因子：
2.4
通讯作者：
VOSCHEPERKEUTER, GH
中科院分区：
文献类型：
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作者：
BENZ, R;SCHMID, A;VOSCHEPERKEUTER, GH
用大肠杆菌外膜的糖特异性LamB（麦芽糖孔蛋白）通道进行脂质双层实验。由LamB引起的电导步骤的单通道分析表明，在水相中的盐浓度和通道电导之间存在线性关系，表明离子和通道内部之间只有很小的结合或没有结合。离子运动通过LamB通道的全部或部分阻断不依赖于水相中的离子浓度。这两个结果允许调查的糖结合更详细，和各种糖的结合到通道内的结合位点的稳定常数计算从滴定实验的膜电导与糖。该通道是高度阳离子选择性的，无论是在存在和不存在的糖，这可能是由于存在的羰基内的通道。这些羰基也可以通过氢键参与糖结合。通过假设一个简单的单位点，两个屏障模型，从M.勒基和H. Nikaido（Proc. Natl. Acad. Sci. USA 77：165-171（1980. alpha.））并给出了糖结合的稳定常数。
Lipid bilayer experiments were performed with the sugar-specific LamB (maltoporin) channel of Escherichia coli outer membrane. Single-channel analysis of the conductance steps caused by LamB showed that there was a linear relationship between the salt concentration in the aqueous phase and the channel conductance, indicating only small or no binding between the ions and the channel interior. The total or the partial blockage of the ion movement through the LamB channel was not dependent on the ion concentration in the aqueous phase. Both results allowed the investigation of the sugar binding in more detail, and the stability constants of the binding of a large variety of sugars to the binding site inside the channel were calculated from titration experiments of the membrane conductance with the sugars. The channel was highly cation selective, both in the presence and absence of sugars, which may be explained by the existence of carbonyl groups inside the channel. These carbonyl groups may also be involved in the sugar binding via hydrogen bonds. The kinetics of the sugar transport through the LamB channel were estimated relative to maltose by assuming a simple one-site, two-barrier model from the relative rates of permeation taken from M. Luckey and H. Nikaido (Proc. Natl. Acad. Sci. USA 77:165-171 (1980.alpha.)) and the stability constants for the sugar binding given in this study.