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λ噬菌体nutL序列突变对N蛋白生物功能的影响 总被引:1,自引:0,他引:1
λ噬菌体 N 蛋白不仅是抗转录终止的正调控因子,也是在翻译水平上阻遏自身基因表达的负调控蛋白.nut R N A 位点(包括 box A 和 box B)参与了这两种生物效应.对位于左向操纵子(p L)的 nut L 序列进行了突变后,证明 nut L 缺失及 box B 第 6 位核苷酸突变使 N 丧失了正、负调控功能,提示 nut L 在 N 介导的调控反应中是必需的.nut L 序列中 box A 单碱基突变使 N 丧失了正调控功能,部分保留了负调控功能.这种负调控作用导至极性效应,使 lac Z基因转录水平明显下降. 相似文献
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Vrentas CE Gaal T Berkmen MB Rutherford ST Haugen SP Vassylyev DG Ross W Gourse RL 《Journal of molecular biology》2008,377(2):551-564
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Daniel J. Koslover Furqan M. Fazal Rachel A. MooneyRobert Landick Steven M. Block 《Journal of molecular biology》2012,423(5):664-676
Rho termination factor is an essential hexameric helicase responsible for terminating 20-50% of all mRNA synthesis in Escherichia coli. We used single-molecule force spectroscopy to investigate Rho-RNA binding interactions at the Rho utilization site of the λtR1 terminator. Our results are consistent with Rho complexes adopting two states: one that binds 57 ± 2 nt of RNA across all six of the Rho primary binding sites, and another that binds 85 ± 2 nt at the six primary sites plus a single secondary site situated at the center of the hexamer. The single-molecule data serve to establish that Rho translocates 5′ → 3′ toward RNA polymerase (RNAP) by a tethered-tracking mechanism, looping out the intervening RNA between the Rho utilization site and RNAP. These findings lead to a general model for Rho binding and translocation and establish a novel experimental approach that should facilitate additional single-molecule studies of RNA-binding proteins. 相似文献
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