The molecular basis for the specificity of fimE in the phase variation of type 1 fimbriae of Escherichia coli K-12.
The molecular basis for the specificity of fimE in the phase variation of type 1 fimbriae of Escherichia coli K-12.
复制标题
fimE 在大肠杆菌 K-12 1 型菌毛相变中的特异性的分子基础。
DOI：
10.1046/j.1365-2958.1999.01257.x
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发表时间：
1999
影响因子：
3.6
通讯作者：
Blomfield,IC
中科院分区：
文献类型：
--
作者：
Kulasekara,HD;Blomfield,IC
大肠杆菌中1型菌毛的表达是可变的，细胞可以在菌毛相（ON）和菌毛相（OFF）之间切换。相位变化依赖于314 bp DNA元件（开关）的取向，该元件经历DNA反转。DNA反转需要在特异性和活性上不同的位点特异性重组酶。而fimb在很少的方向偏差下促进重组，而time只在ON - to - OFF方向上促进重组。在野生型细胞中，time活性占主导地位，因此，大多数细菌都是半溶菌。本文表明，特异性是由两种不同但互补的机制引起的。首先，time表现出对ON取向开关作为重组基板的强烈偏好。重组酶结合位点的核苷酸序列差异是决定FimE特异性的关键因素，尽管FimE开关旁边的一个或多个额外的cis活性位点似乎也参与其中。其次，开关的方向在cis中控制时间，很可能控制重组酶的表达。
The expression of type 1 fimbriae inEscherichia coliis phase variable, with cells switching between fimbriate (ON) and afimbriate (OFF) phases. The phase variation is dependent on the orientation of a 314 bp DNA element (the switch) that undergoes DNA inversion. DNA inversion requires eitherfimBorfimE, site‐specific recombinases that differ in both specificity and activity. WhereasfimBpromotes recombination with little orientational bias,fimEpromotes recombination in the ON‐to‐OFF direction exclusively. In wild‐type cells,fimEactivity predominates and, hence, most bacteria are afimbriate. Here, it is shown thatfimEspecificity is caused by two different, but complementary, mechanisms. First, FimE shows a strong preference for the switch in the ON orientation as a substrate for recombination. Differences in the nucleotide sequence of the recombinase binding sites is a key factor in determining FimE specificity, although one or more additionalcis‐active sites that flank thefimswitch also appear to be involved. Secondly, the orientation of the switch controlsfimE in cis, most probably to control recombinase expression.