The mechanism of inducer exclusion. Direct interaction between purified IIIGlc of the phosphoenolpyruvate:sugar phosphotransferase system and the lactose carrier of Escherichia coli
The mechanism of inducer exclusion. Direct interaction between purified IIIGlc of the phosphoenolpyruvate:sugar phosphotransferase system and the lactose carrier of Escherichia coli
复制标题
诱导物排除机制。
DOI：
10.1002/j.1460-2075.1983.tb01490.x
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发表时间：
1983
期刊：
影响因子：
--
通讯作者：
Pieter W. Postma
中科院分区：
文献类型：
--
作者：
S. O. Nelson;J. K. Wright;J. K. Wright;Pieter W. Postma
通过细菌磷酸烯醇丙酮酸调节某些糖转运系统的假说：糖转运系统假定该系统的IIIGlc与其活性受到调节的载体之间存在相互作用。我们已经研究了这种相互作用更详细，采用这些运输系统之一，乳糖载体的大肠杆菌。磷酸转移酶系统的纯化IIIGlc直接与乳糖载体相互作用。IIIGlc与乳糖载体的结合需要存在IIIGlc的非磷酸化形式和载体的底物，并且表现出1.2± 0.2 mol IIIGlc/mol乳糖载体的化学计量。乳糖载体对IIIGlc的Kd为10 ± 5 µM。IIIGlc显然不能与突变型乳糖载体相互作用，所述突变型乳糖载体仍然结合但不转运半乳糖苷。IIIGlc与乳糖载体的结合导致半乳糖苷对载体的表观亲和力增加3.5倍。值得注意的是，IIIGlc与乳糖载体的结合导致在用纯化的乳糖载体重构的膜囊泡和脂质体中半乳糖苷易位的抑制。因此，这种抑制可能是诱导物排斥现象的基础。
A hypothesis for the regulation of some sugar transport systems by the bacterial phosphoenolpyruvate:sugar transport system postulates an interaction between IIIGlc of this system and the carrier whose activity is regulated. We have studied this interaction in more detail, employing one of these transport systems, the lactose carrier of Escherichia coli. Purified IIIGlc of the phosphotransferase system interacted directly with the lactose carrier. The binding of IIIGlc to lactose carrier required the presence of the non‐phosphorylated form of IIIGlc and substrates of the carrier and exhibited a stoichiometry of 1.2± 0.2 mol IIIGlc/mol lactose carrier. The Kd of lactose carrier for IIIGlc was 10 ± 5 µM. IIIGlc is apparently unable to interact with a mutant lactose carrier which still binds but does not transport galactosides. The binding of IIIGlc to the lactose carrier results in a 3.5‐fold increase in the apparent affinity of galactosides for the carrier. Significantly, the binding of IIIGlc to the lactose carrier results in an inhibition of galactoside translocation both in membrane vesicles and liposomes reconstituted with the purified lactose carrier. This inhibition may thus be the basis for the well‐documented phenomenon of inducer exclusion.