REGULATION OF FERRIC IRON TRANSPORT IN ESCHERICHIA-COLI-K12 - ISOLATION OF A CONSTITUTIVE MUTANT
REGULATION OF FERRIC IRON TRANSPORT IN ESCHERICHIA-COLI-K12 - ISOLATION OF A CONSTITUTIVE MUTANT
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DOI：
10.1007/bf00269672
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发表时间：
1981-01-01
期刊：
影响因子：
--
通讯作者：
HANTKE, K
中科院分区：
文献类型：
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作者：
HANTKE, K
用噬菌体Mu（Ap，lac）将lac基因插入到指定Fe吸收系统组分的fhuA、fepA、cir和tonB基因中。在所有这些操纵子融合体中，乳糖的表达受Fe对细胞的可用性控制，这有助于快速简单地测量上述基因的表达。在厌氧条件下的富铁培养基中，所有系统都受到强烈抑制。fhuA在较高的铁浓度下比fepA或cir受到抑制，而tonB仅在厌氧条件下受到抑制，并且可以通过铁限制来诱导。组成性表达β-在fhuA-lac融合菌株中选择半乳糖苷酶。在这些突变株中，外膜蛋白Cir、FhuA、FecA、76 K和83 K是组成型的。他们被称为毛皮变种人。在这些毛皮突变株中，19 K蛋白的合成减少。铁肠螯合素和铁色素的转运显然在毛皮突变细胞中也是组成性的，并且与野生型细胞相比，在生长培养基中仅10 μ M柠檬酸盐就可以诱导柠檬酸铁摄取，在野生型细胞中需要至少100 μ M柠檬酸盐。fepA基因受到额外的控制，因为它没有被毛皮突变完全去抑制。
The lac genes were inserted with phage Mu(Ap, lac) into the fhuA, fepA, cir and tonB genes which specify components of Fe uptake systems. The expression of lac in all these operon fusions was controlled by the availability of Fe to the cells, facilitating a quick and simple measurement of the expression of the genes listed above. In an Fe-rich medium under anaerobic conditions all systems were strongly repressed. fhuA was depressed at higher Fe concentration than was fepA or cir, and tonB was repressed only under anaerobic conditions and could be induced by Fe limitation. Mutants constitutive for the expression of .beta.-galactosidase were selected in a fhuA-lac fusion strain. The outer membrane proteins Cir, FhuA, FecA, 76K and 83K were made constitutively in such mutant strains. They were termed fur mutants. In these fur mutant strains the synthesis of a 19K protein was reduced. Transport of ferric enterochelin and ferrichrome apparently was also constitutive in the fur mutant cells, and ferric citrate uptake could be induced by only 10 .mu.M citrate in the growth medium in contrast to wild-type cells in which at least 100 .mu.M citrate was necessary. The fepA gene was under an additional control, because it was not fully derepressed by the fur mutation.