González-Pérez M Mar, Marqués Silvia, Domínguez-Cuevas Patricia, Ramos Juan L
Department of Biochemistry and Molecular and Cellular Biology of Plants, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, C/Profesor Albareda 1, Granada, Spain.
FEBS Lett. 2002 May 22;519(1-3):117-22. doi: 10.1016/s0014-5793(02)02730-8.
Transcription from the TOL plasmid meta-cleavage pathway operon, Pm, depends on the XylS protein being activated by a benzoate effector. The XylS binding sites are two imperfect 5'-TGCAN(6)GGNTA-3' direct repeats located between positions -70/-56 and -49/-35 [González-Pérez et al. (1999) J. Biol. Chem. 274, 2286-2290]. An intrinsic bending of 40 degrees, which is not essential for transcription, is centered at position -43. We have determined the potential overlap between the XylS and RNA polymerase binding sites. The insertion of 2 or more bp between C and T at positions -37 and -36 abolished transcription activation by the wild-type XylS and by XylSS229I, a mutant with increased affinity for the XylS binding sites. In contrast, a 1-bp insertion at -37 was permissible, although when in addition to the 1-bp insertion at -37 the mutant promoter had a point mutation at the XylS binding site (C-47-->T), transcription was abolished with the wild-type XylS protein, but not with XylSS229I. The overlap between the proximal XylS binding site and the -35 region recognized by RNA polymerase at positions -35 and -36 appears to be critical for transcription.
来自TOL质粒间位裂解途径操纵子Pm的转录取决于苯甲酸酯效应物激活的XylS蛋白。XylS结合位点是位于-70 / -56和-49 / -35位置之间的两个不完全的5'-TGCAN(6)GGNTA-3'直接重复序列[González-Pérez等人（1999年）《生物化学杂志》274, 2286 - 2290]。一个40度的固有弯曲（对转录不是必需的）以-43位置为中心。我们已经确定了XylS和RNA聚合酶结合位点之间的潜在重叠。在-37和-36位置的C和T之间插入2个或更多碱基对消除了野生型XylS和XylSS229I（一种对XylS结合位点亲和力增加的突变体）的转录激活。相比之下，在-37位置插入1个碱基对是允许的，尽管除了在-37位置插入1个碱基对外，突变启动子在XylS结合位点（C-47→T）还有一个点突变，但野生型XylS蛋白会消除转录，而XylSS229I则不会。近端XylS结合位点与RNA聚合酶在-35和-36位置识别的-35区域之间的重叠似乎对转录至关重要。
