Pellicer M T, Fernandez C, Badía J, Aguilar J, Lin E C, Baldom L
Department of Biochemistry, School of Pharmacy, University of Barcelona, Avenida Diagonal 643, 08028 Barcelona, Spain.
J Biol Chem. 1999 Jan 15;274(3):1745-52. doi: 10.1074/jbc.274.3.1745.
The metabolic pathways specified by the glc and ace operons in Escherichia coli yield glyoxylate as a common intermediate, which is acted on by two malate synthase isoenzymes: one encoded by glcB and the other by aceB. Null mutations in either gene exhibit no phenotype, because of cross-induction of the ace operon by glycolate and the glc operon by acetate. In this study, the regulation of the glc operon, comprising the structural genes glcDEFGB, was analyzed at the molecular level. This operon, activated by growth on glycolate, is transcribed as a single message and is under the positive control of GlcC encoded by a divergent gene. Expression of the glc operon is strongly dependent on the integration host factor (IHF) and is repressed by the global respiratory regulator ArcA-P. In vitro gel-shift experiments demonstrated direct binding of the promoter DNA to IHF and ArcA-P. Mutant analysis indicated that cross-induction of the glc operon by acetate is mediated by the GlcC protein that recognizes the compound as an alternative effector. The similar pattern of regulation of the Glc and Ace systems by IHF and ArcA-P ensures their effective cross-induction.
大肠杆菌中由glc和ace操纵子指定的代谢途径产生乙醛酸作为共同中间体，乙醛酸由两种苹果酸合酶同工酶作用：一种由glcB编码，另一种由aceB编码。任一基因的无效突变均无表型，这是因为乙醇酸对ace操纵子的交叉诱导以及乙酸盐对glc操纵子的交叉诱导。在本研究中，对包含结构基因glcDEFGB的glc操纵子的调控进行了分子水平分析。该操纵子在以乙醇酸为碳源生长时被激活，作为单一转录本进行转录，并受由一个 divergent 基因编码的GlcC的正调控。glc操纵子的表达强烈依赖于整合宿主因子（IHF），并受全局呼吸调节因子ArcA-P的抑制。体外凝胶迁移实验证明启动子DNA与IHF和ArcA-P直接结合。突变分析表明，乙酸盐对glc操纵子的交叉诱导是由将该化合物识别为替代效应物的GlcC蛋白介导的。IHF和ArcA-P对Glc和Ace系统的类似调控模式确保了它们的有效交叉诱导。
