THE 3 OPERATORS OF THE LAC OPERON COOPERATE IN REPRESSION
THE 3 OPERATORS OF THE LAC OPERON COOPERATE IN REPRESSION
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DOI：
10.1002/j.1460-2075.1990.tb08199.x
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发表时间：
1990-04-01
期刊：
影响因子：
11.4
通讯作者：
MULLERHILL, B
中科院分区：
文献类型：
--
作者：
OEHLER, S;EISMANN, ER;MULLERHILL, B
我们测试了系统性破坏大肠杆菌染色体 lac 操纵子的所有三个 lac 操纵子对 Lac 阻遏物抑制的影响。仅一个“伪操纵子”O2 或 O3 的缺失使野生型四聚 Lac 阻遏物的抑制降低约 2 至 3 倍；两个“伪操纵子”的缺失使抑制降低 > 50 倍。在这些条件下单独的 O1 仅抑制约 20 倍。二聚体活性 Lac 阻遏物 (iadi) 抑制野生型 lac这表明 lac 操纵子之间的协同相互作用是由于四聚体 Lac 阻遏物介导的 DNA 环形成，在不可能形成环的条件下，占据 O3 而不是 O2 可能会导致弱抑制，这表明在这些条件下 CAP 激活可能会受到抑制，并且在 O2 处停止转录不会显着促进抑制。
We tested the effect of systematic destruction of all three lac operators of the chromosomal lac operon of Escherichia coli on repression by Lac repressor. Absence of just one "pseudo-operator'' O2 or O3 decreases repression by wild-type tetrameric Lac repressor .apprx. 2- to-3-fold; absence of both ''pseudo-operators'' decreases repression > 50-fold. O1 alone represses under these conditions only .apprx. 20-fold. Dimeric active Lac repressor (iadi) represses the wild-type lac operon to about the same low extent. This indicates that cooperative interaction between lac operators is due to DNA loop formation mediated by tetrameric Lac repressor. Under conditions where loop formation is impossible, occupation of O3 but not of O2 may lead to weak repression. This suggests that under these conditions CAP activation may be inhibited and that stopping transcription at O2 does not significantly contribute to repression.