Chang M, Crawford I P
Department of Microbiology, University of Iowa, Iowa City 52242.
Nucleic Acids Res. 1990 Feb 25;18(4):979-88. doi: 10.1093/nar/18.4.979.
The TrpI protein belongs to the LysR-family of procaryotic regulatory proteins. Members of this family share a characteristic similarity of their N-terminal amino acid sequences, and many of them are activators of divergently transcribed genes or operons. In Pseudomonas aeruginosa, the genes for tryptophan synthase, trpBA, are regulated by indoleglycerol phosphate (InGP) and TrpI. We demonstrate here that in the absence of InGP, the binding site of TrpI is located in the -52 to -77 region of the trpBA promoter; in the presence of InGP, the binding region is extended to the -32 region. In addition, two major, slow moving protein-DNA complexes are seen in gel retardation assays: the faster moving complex is formed in the absence of InGP and the amount of the slower moving complex is greatly enhanced in the presence of InGP. These results suggest that the binding of a second TrpI protein molecule, promoted by InGP, plays a crucial role in activating the expression of the trpBA gene pair.
色氨酸I（TrpI）蛋白属于原核生物调节蛋白的LysR家族。该家族成员的N端氨基酸序列具有特征性相似性，其中许多是反向转录基因或操纵子的激活剂。在铜绿假单胞菌中，色氨酸合酶基因trpBA受吲哚甘油磷酸（InGP）和TrpI调控。我们在此证明，在没有InGP的情况下，TrpI的结合位点位于trpBA启动子的-52至-77区域；在有InGP的情况下，结合区域延伸至-32区域。此外，在凝胶阻滞试验中可观察到两种主要的、迁移缓慢的蛋白质-DNA复合物：迁移较快的复合物在没有InGP的情况下形成，而迁移较慢的复合物的量在有InGP的情况下大大增加。这些结果表明，由InGP促进的第二个TrpI蛋白分子的结合在激活trpBA基因对的表达中起关键作用。
