Piñeiro S, Olekhnovich I, Gussin G N
Department of Biological Sciences, University of Iowa, Iowa City 52242, USA.
J Bacteriol. 1997 Sep;179(17):5407-13. doi: 10.1128/jb.179.17.5407-5413.1997.
TrpI protein, the activator of transcription of the trpBA operon of fluorescent pseudomonads, bends the DNA when it forms either of two well-characterized complexes with the trpBA regulatory region. In complex 1, with TrpI bound only to its strong binding site (site I), the calculated bending angle is 65 to 67 degrees and the center of bending is in the middle of site I. In complex 2, which is required for activation of the trpBA promoter, with TrpI bound both to site I and to the weaker site II, the bending angle is increased to 89 to 90 degrees and the center of bending is at the site I-site II boundary. Indoleglycerol phosphate (InGP), which strongly stimulates formation of complex 2 and is required for activation, does not affect the bending angle of either complex. However, a mutation (-10C/11C) shown previously to affect activation has a small but detectable effect on bending, reducing the calculated bending angle to 83 to 86 degrees. These results suggest a way that DNA bending and InGP may be important for activation.
色氨酸I蛋白是荧光假单胞菌trpBA操纵子转录的激活因子，当它与trpBA调控区形成两种特征明确的复合物中的任何一种时，都会使DNA弯曲。在复合物1中，色氨酸I仅与它的强结合位点（位点I）结合，计算出的弯曲角度为65至67度，弯曲中心在位点I的中间。在复合物2中，trpBA启动子激活需要该复合物，色氨酸I既结合在位点I上，也结合在较弱的位点II上，弯曲角度增加到89至90度，弯曲中心在位点I - 位点II边界处。磷酸吲哚甘油（InGP）强烈刺激复合物2的形成且是激活所必需的，但它不影响任何一种复合物的弯曲角度。然而，先前显示影响激活的一个突变（-10C/11C）对弯曲有微小但可检测到的影响，将计算出的弯曲角度降低到83至86度。这些结果表明了一种DNA弯曲和InGP可能对激活很重要的方式。
