Proton-linked L-rhamnose transport, and its comparison with L-fucose transport in Enterobacteriaceae.
Proton-linked L-rhamnose transport, and its comparison with L-fucose transport in Enterobacteriaceae.
复制标题
肠杆菌中质子连接的 L-鼠李糖转运及其与 L-岩藻糖转运的比较。
作者：
J. A. Muiry;T. Gunn;T. McDonald;S. Bradley;C. Tate;P. Henderson
1. 当l -鼠李糖、l -甘露糖或l -葡萄糖加入l -鼠李糖培养的能量耗尽型大肠杆菌悬浊液时，pH值发生碱性变化。这是糖- h +同位体活性的诊断。2. L-鼠李糖、L-甘露糖和L-葡萄糖是糖- h +同调和L-[14C]鼠李糖转运活性的诱导剂。L-鼠李糖在L-鼠李糖代谢的菌株中也能诱导出生物化学和遗传上不同的L- focus - h +同调活性。3. 稳态动力学测量表明，L-甘露糖和L-葡萄糖是L-鼠李糖转运系统的竞争性抑制剂（替代底物），L-半乳糖和d -阿拉伯糖是L-聚焦转运系统的竞争性抑制剂（替代底物）。与其他相关结构的糖的额外测量确定了两种运输系统的不同底物特异性。4. H+同运和糖代谢的相对速率及其动力学参数的相对值表明，转运活性的生理作用主要是利用l -鼠李糖，而不是利用l -甘露糖或l -葡萄糖。5. l -鼠李糖转运到大肠杆菌亚细胞囊泡依赖于呼吸作用，在pH为7时转运效果最佳，并受到质子载体和离子载体的抑制。对n -乙基马来酰亚胺和细胞松弛素B. 6不敏感。l -鼠李糖、l -甘露糖和l -葡萄糖分别被添加到l -鼠李糖培养的鼠伤寒沙门氏菌LT2、肺炎克雷伯菌、产气克雷伯菌、胡萝卜欧文菌和腐败胡萝卜欧文菌的能量耗尽悬浊液中，引起碱性pH值的变化。随后酸化的相对速率因生物体和糖的不同而不同。L-聚焦促进了L-鼠李糖诱导的所有生物的碱性pH变化，除了欧文菌。L-鼠李糖- h +不存在于任何生长在L-病灶上的生物体中。7. 这些结果表明，L-鼠李糖转运到微生物体内的过程与L-聚焦转运不同。这两种系统都是由质子的跨膜电化学梯度激发的。8. 稳态动力学测量和结合蛋白分析均未显示大肠杆菌中存在第二种l -鼠李糖转运系统。
1. An alkaline pH change occurred when L-rhamnose, L-mannose or L-lyxose was added to L-rhamnose-grown energy-depleted suspensions of strains of Escherichia coli. This is diagnostic of sugar-H+ symport activity. 2. L-Rhamnose, L-mannose and L-lyxose were inducers of the sugar-H+ symport and of L-[14C]rhamnose transport activity. L-Rhamnose also induced the biochemically and genetically distinct L-fucose-H+ symport activity in strains competent for L-rhamnose metabolism. 3. Steady-state kinetic measurements showed that L-mannose and L-lyxose were competitive inhibitors (alternative substrates) for the L-rhamnose transport system, and that L-galactose and D-arabinose were competitive inhibitors (alternative substrates) for the L-fucose transport system. Additional measurements with other sugars of related structure defined the different substrate specificities of the two transport systems. 4. The relative rates of H+ symport and of sugar metabolism, and the relative values of their kinetic parameters, suggested that the physiological role of the transport activity was primarily for utilization of L-rhamnose, not for L-mannose or L-lyxose. 5. L-Rhamnose transport into subcellular vesicles of E. coli was dependent on respiration, was optimal at pH 7, and was inhibited by protonophores and ionophores. It was insensitive to N-ethylmaleimide or cytochalasin B. 6. L-Rhamnose, L-mannose and L-lyxose each elicited an alkaline pH change when added to energy-depleted suspensions of L-rhamnose-grown Salmonella typhimurium LT2, Klebsiella pneumoniae, Klebsiella aerogenes, Erwinia carotovora carotovora and Erwinia carotovora atroseptica. The relative rates of subsequent acidification varied, depending on both the organism and the sugar. L-Fucose promoted an alkaline pH change in all the L-rhamnose-induced organisms except the Erwinia species. No L-rhamnose-H+ symport occurred in any organism grown on L-fucose. 7. All these results showed that L-rhamnose transport into the micro-organisms occurred by a system different from that for L-fucose transport. Both systems are energized by the trans-membrane electrochemical gradient of protons. 8. Neither steady-state kinetic measurements nor binding-protein assays revealed the existence of a second L-rhamnose transport system in E. coli.