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首页> 外文期刊>Journal of bacteriology >Exogenous induction of the Escherichia coli hexose phosphate transport system defined by uhp-lac operon fusions.
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Exogenous induction of the Escherichia coli hexose phosphate transport system defined by uhp-lac operon fusions.

机译：由uhp-lac操纵子融合定义的大肠杆菌己糖磷酸转运系统的外源诱导。

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The uhp-coded hexose phosphate transport system of Escherichia coli is normally induced by the presence of extracellular glucose-6-phosphate (G6P), whereas internally generated G6P does not provide a regulatory signal. Strains carrying uhp-lac operon fusions in which lac operon expression is under the control of the uhpT promoter were isolated. The direction of transcription of the uhp T gene was found to be counterclockwise on the E. coli chromosome map. The effects of added sugar phosphates on induction of beta-galactosidase and G6P uptake activities were compared in two fusion-carrying strains differing only in the presence of functional Uhp+ activity. Induction of uhp expression by G6P was equally effective in the two strains; accumulation of G6P diminished its ability to serve as an inducer. Mannose-6-phosphate was an effective competitive inhibitor of G6P uptake, but did not inhibit induction by G6P of uhp expression. No sugar phosphates were found that inhibited induction by G6P. Inorganic phosphate competitively inhibited induction by G6P whether G6P transport activity was present or not. Thus, the transport activity is not involved in the regulation of its synthesis, and these results strongly support the view that the uhp regulatory system senses only the external environment.
机译：大肠杆菌的uhp编码的磷酸己糖磷酸转运系统通常是由细胞外6-磷酸葡萄糖（G6P）诱导而产生的，而内部产生的G6P不提供调节信号。分离了携带uhp-lac操纵子融合体的菌株，其中lac操纵子的表达在uhpT启动子的控制下。发现uhp T基因的转录方向在大肠杆菌染色体图谱上是逆时针方向。在仅具有功能性Uhp +活性的情况下，在两种融合携带菌株中比较了添加的糖磷酸酯对β-半乳糖苷酶诱导和G6P摄取活性的影响。 G6P诱导uhp表达在两种菌株中均有效。 G6P的积累降低了其作为诱导物的能力。 6-磷酸甘露糖是G6P摄取的有效竞争抑制剂，但不抑制uhp表达的G6P诱导。没有发现糖磷酸酯抑制G6P的诱导。无论是否存在G6P转运活性，无机磷酸盐都可竞争性地抑制G6P的诱导。因此，运输活动不参与其合成的调控，这些结果有力地支持了uhp调控系统仅感知外部环境的观点。

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