Integration host factor stimulates both FimB- and FimE-mediated site-specific DNA inversion that controls phase variation of type 1 fimbriae expression in Escherichia coli
Integration host factor stimulates both FimB- and FimE-mediated site-specific DNA inversion that controls phase variation of type 1 fimbriae expression in Escherichia coli
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DOI：
10.1046/j.1365-2958.1997.2241615.x
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发表时间：
1997-02-01
影响因子：
3.6
通讯作者：
Eisenstein, BI
中科院分区：
文献类型：
--
作者：
Blomfield, IC;Kulasekara, DH;Eisenstein, BI
控制大肠杆菌1型菌毛相位变异的位点特异性DNA倒位。大肠杆菌中的重组酶由两种重组酶FimB和FimE催化。通过任一重组酶的有效转化也需要亮氨酸响应调节蛋白（Lrp）。此外，FimB重组由整合宿主因子（IHF）刺激。IHF对FimE转化的影响以前没有报道过。在这里，它表明，IHF刺激FimE重组;在菌株MG 1655中，突变体中的任何一个的α（ihfA）或β（ihfB）的IHF亚基损伤显示FimB（100倍）和FimE（15000倍）促进开关显着减少。显示IHF以高亲和力结合至与膜可逆元件相邻的位点（位点I）和膜可逆元件内的位点（位点II）。此外，发现降低体外IHF结合亲和力的位点I或位点II中的突变降低体内FimE和/或FimB重组的频率。虽然位点I和位点II突变组合对FimB促进的转换的影响与IHF敲除突变的影响相当（100倍），但顺式位点突变对FimE促进的转换的影响要小得多（100倍）。
The site-specific DNA inversion that controls phase variation of type 1 fimbriation in E. coli is catalysed by two recombinases, FimB and FimE. Efficient inversion by either recombinase also requires the leucine-responsive regulatory protein (Lrp). In addition, FimB recombination is stimulated by the integration host factor (IHF). The effect of IHF on FimE inversion has not previously been reported. Here it is shown that IHF stimulates FimE recombination; in strain MG1655, mutants containing lesions in either the alpha (ihfA) or beta (ihfB) subunits of IHF show a marked decrease in both FimB- (100-fold) and FimE (15000-fold)-promoted switching. IHF is shown to bind with high affinity to sites both adjacent to (site I) and within (site II) the fim invertible element. Furthermore, mutations in site I or site II that lower the affinity of IHF binding in vitro were found to lower the frequency of FimE and/or FimB recombination in vivo. Although site I and site II mutations in combination have an effect on FimB-promoted switching comparable to that of IHF knockout mutations (100-fold), the cis site mutations have a much less marked effect (100-fold) on FimE-promoted switching.