STABLE ALBICIDIN RESISTANCE IN ESCHERICHIA-COLI INVOLVES AN ALTERED OUTER-MEMBRANE NUCLEOSIDE UPTAKE SYSTEM
STABLE ALBICIDIN RESISTANCE IN ESCHERICHIA-COLI INVOLVES AN ALTERED OUTER-MEMBRANE NUCLEOSIDE UPTAKE SYSTEM
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DOI：
10.1099/00221287-136-1-51
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发表时间：
1990-01-01
期刊：
影响因子：
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通讯作者：
BASNAYAKE, WV
中科院分区：
文献类型：
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作者：
BIRCH, RG;PEMBERTON, JM;BASNAYAKE, WV
Albicidin阻断PolA-EndA-大肠杆菌菌株的完整细胞中的DNA合成，以及提供了所有必需的前体核苷酸的透化细胞中的DNA合成，表明对原核生物DNA复制的直接影响。albicidin对albicidin敏感的大肠杆菌（Alb 5）中的T4和T7的复制也有抑制作用，但对albicidin耐药的大肠杆菌（Albr）中的T4和T7的复制无影响。coli宿主细胞。所有稳定的自发Albr突变株均为E.大肠杆菌同时对噬菌体T76产生抗性。确定albicidin敏感性的位点位于tsx，tsx是用作噬菌体T6受体的外膜蛋白的结构基因，参与以亚微摩尔细胞外浓度存在的核苷通过外膜的运输。Albicidin在结构上与核苷并不十分相似。而Alb 5 E.大肠杆菌菌株从周围培养基中快速积累核苷和albicidin，而Albr突变体在低细胞外浓度下摄取核苷和albicidin方面有缺陷。插入突变阻断Tsx蛋白产生也阻断albicidin摄取并传递albicidin抗性。在完整的Alb 5 E中，以约0.1 μ M提供的白纹菌素在数秒内阻断DNA复制。coli细胞，但100倍更高的albicidin浓度是必要的，以快速抑制DNA复制透化细胞。我们得出结论，albicidin在很低的浓度下对E.因为它通过通常参与核苷摄取的TSX编码的外膜通道的非法转运而在细胞内迅速浓缩。Albicidin抗性是由于albicidin通过外膜转运机制的丧失。
Albicidin blocked DNA synthesis in intact cells of a PolA- EndA- Escherichia coli strain, and in permeabilized cells supplied with all necessary precursor nucleotides, indicating a direct effect on prokaryote DNA replication. Replication of phages T4 and T7 was also blocked by albicidin in albicidin-sensitive (Alb5) but not in albicidin-resistant (Albr) E. coli host-cells. All stable sponaneous Albr mutants of E. coli simultaneously became resistance to phage T76. The locus determining albicidin sensitivity mapped at tsx, the structural gene for an outer-membrane protein used as a receptor by phage T6 and involved in transport through the outer membrane of nucleosides present at submicromolar extracellular concentrations. Albicidin does not closely resemble a nucleoside in structure. However, Alb5 E. coli strains rapidly accumulated both nucleosides and albicidin from the surrounding medium whereas the Albr mutants were defective in uptake of nucleosides and albicidin at low extracellular concentrations. An insertion mutation blocked Tsx protein production also blocked albicidin uptake and conveyed albicidin resistance. Albicidin supplied at approximately 0.1 .mu.M blocked DNA replication within seconds in intact Alb5 E. coli cells, but a 100-fold higher albicidin concentrations was necessary for a rapid inhibition of DNA replication in permeabilized cells. We conclude that albicidin is effective at very low concentrations against E. coli because it is rapidly concentrated within cells by illicit transport through the tsx-encoded outer-membrane channel normally involved in nucleoside uptake. Albicidin resistance results from loss of the mechanism of albicidin transport through the outer membrane.