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首页> 外文期刊>Journal of bacteriology >YfiK from Escherichia coli Promotes Export of O-Acetylserine and Cysteine
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YfiK from Escherichia coli Promotes Export of O-Acetylserine and Cysteine

机译：大肠杆菌的YfiK促进O-乙酰丝氨酸和半胱氨酸的出口

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yfiK was discovered as a gene augmenting cysteine production when it was overexpressed in an industrial Escherichia coli production strain. The gene product is an integral membrane protein with about six predicted transmembrane helices; it belongs to the RhtB family of export proteins. YfiK overproduction from a plasmid leads to drastic and parallel secretion of O-acetylserine and cysteine into the medium but only when the organism possesses a serine transacetylase that is feedback insensitive to cysteine. Externally provided O-acetylserine obviated this requirement for cysteine secretion both in the yfiK-carrying transformant and in the wild type. A ΔyfiK mutant did not show any phenotype, and it exported O-acetylserine and cysteine when transformed with a plasmid carrying ydeD, a previously characterized, alternate O-acetylserine/cysteine exporter. Since a ydeD-yfiK double mutant showed the same pattern, it appears that YfiK and YdeD act independently. The necessity for the cell to regulate the size of the internal pool of O-acetylserine via synthesis of exporter proteins could be connected to the fact that this compound (when supplied externally) inhibits growth. Overexpression of either ydeD or yfiK leads to alleviation of this inhibition paralled by increased resistance to azaserine, which is an analog of O-acetylserine.
机译：当 yfiK 在工业大肠杆菌生产菌株中过表达时，它被发现是增加半胱氨酸生产的基因。该基因产物是具有约六个预测跨膜螺旋的完整膜蛋白;其中一个是膜蛋白。它属于RhtB出口蛋白家族。从质粒产生的YfiK过量会导致 O -乙酰丝氨酸和半胱氨酸大量平行分泌到培养基中，但仅当生物体具有对半胱氨酸反馈不敏感的丝氨酸转乙酰酶时才如此。外部提供的 O -乙酰丝氨酸消除了携带 yfiK 的转化子和野生型中对半胱氨酸分泌的要求。一个ΔyfiK突变体没有表现出任何表型，并且在用带有 ydeD 的质粒进行转化后输出了 O -乙酰丝氨酸和半胱氨酸， O -乙酰丝氨酸/半胱氨酸的替代出口商。由于 ydeD-yfiK 双重突变体显示出相同的模式，因此YfiK和YdeD似乎独立起作用。细胞通过合成输出蛋白来调节 O -乙酰丝氨酸内部库大小的必要性可能与该化合物（从外部提供）抑制生长这一事实有关。 ydeD 或 yfiK 的过度表达可减轻这种抑制作用，而这种抑制作用是由于对azaserine的抗性增加而引起的，而azaserine是 O -乙酰丝氨酸的类似物。

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