Regulation of the maltose transport system of Escherichia coli by the glucose-specific enzyme III of the phosphoenolpyruvate-sugar phosphotransferase system. Characterization of inducer exclusion-resistant mutants and reconstitution of inducer exclusion in proteoliposomes.
Regulation of the maltose transport system of Escherichia coli by the glucose-specific enzyme III of the phosphoenolpyruvate-sugar phosphotransferase system. Characterization of inducer exclusion-resistant mutants and reconstitution of inducer exclusion in proteoliposomes.
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磷酸烯醇丙酮酸-糖磷酸转移酶系统的葡萄糖特异性酶 III 对大肠杆菌麦芽糖转运系统的调节。
DOI：
10.1016/s0021-9258(17)45318-x
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发表时间：
1990
期刊：
影响因子：
--
通讯作者：
M. H. Saier
中科院分区：
文献类型：
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作者：
David A. Dean;J. Reizer;Hiroshi Nikaido;M. H. Saier
麦芽糖在大肠杆菌中的转运是由磷酸烯醇丙酮酸-糖磷酸转移酶系统中的葡萄糖特异性酶III （IIIglc）在蛋白质水平上调节的，其机制被称为诱导剂排斥。我们分离并鉴定了麦芽糖转运系统中的四个突变体，它们都在malK中，它们对诱导剂排斥具有抗性。其中三个突变体的突变落在MalK的cooh末端结构域内，并提示该结构域的首次报道功能。其中两个位于与lacY和melB序列相似的区域，这两个区域也受IIIglc调控，因此可能定义了IIIglc结合域。我们还在麦芽糖渗透酶过表达膜制备的蛋白脂质体中重建了诱导剂排除。当IIIglc包含在囊泡内时，麦芽糖转运被抑制50-60%。这种抑制是由于运输的Vmax减少了2倍。IIIglc不影响ATP水解与麦芽糖运输的偶联，因为在存在和不存在IIIglc的情况下，ATP水解/麦芽糖运输的比例保持不变。最后，IIIglc的Ki值为40微米，与IIIglc的体内浓度基本一致。
Maltose transport in Escherichia coli is regulated at the protein level by the glucose-specific enzyme III (IIIglc) of the phosphoenolpyruvate-sugar phosphotransferase system, by a mechanism known as inducer exclusion. We have isolated and characterized four mutants in the maltose transport system, all of which are in malK, which are resistant to inducer exclusion. The mutations in three of these mutants fall within the COOH-terminal domain of MalK and suggest the first reported function for this domain. Two of these are in a region which shows sequence similarity to lacY and melB, both of which are also regulated by IIIglc, and thus may define a IIIglc-binding domain. We have also reconstituted inducer exclusion in proteoliposomes made from membranes overexpressing the maltose permease. Maltose transport is inhibited by 50-60% when IIIglc is included in the intravesicular space. The inhibition is due to a decrease in the Vmax of transport by a factor of 2. IIIglc does not affect the coupling of ATP hydrolysis to maltose transport, since the ratio of ATP hydrolyzed/maltose transported remained constant in the presence and absence of IIIglc. Finally, the Ki for IIIglc was 40 microM, roughly the same as the in vivo concentration of IIIglc.