Structure of inhibited fructose-1,6-bisphosphatase from Escherichia coli -: Distinct allosteric inhibition sites for AMP and glucose 6-phosphate and the characterization of a gluconeogenic switch
Structure of inhibited fructose-1,6-bisphosphatase from Escherichia coli -: Distinct allosteric inhibition sites for AMP and glucose 6-phosphate and the characterization of a gluconeogenic switch
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DOI：
10.1074/jbc.m703580200
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发表时间：
2007-08-24
影响因子：
4.8
通讯作者：
Honzatko, Richard B.
中科院分区：
文献类型：
--
作者：
Hines, Justin K.;Kruesel, Claire E.;Honzatko, Richard B.
磷酸烯醇式丙酮酸对大肠杆菌果糖-1，6-二磷酸酶的变构激活意味着异养细菌中异源生成的快速前馈激活。但是，这些细菌是如何快速下调激活的FBPase以避免无效的循环的呢？这里显示的是E.葡萄糖6-磷酸（Glc-6-P）是葡萄糖转运进入细胞后产生的第一个代谢产物。响应于Glc-6-P和AMP连接，FBPase经历从典型R-状态到T-样状态的四级转变。通过置换Phe（15），AMP结合到与哺乳动物FBPase相当的变构位点。螺旋H1和H2的相对运动干扰磷酸烯醇丙酮酸的变构激活位点。Glc-6-P结合到以前结构中未观察到的变构位点，干扰成对形成FBPase完整活性位点的亚基。Glc-6-P和AMP是大肠杆菌的协同抑制剂。大肠杆菌FBPase，将细菌中的AMP/Glc-6-P抑制作为哺乳动物FBPase中AMP/果糖2，6-二磷酸抑制的可能进化前身。毫无例外，变构活化的特征残基与Glc-6-P位点的关键残基一起沿着出现在细菌序列中。这些生物体中的FBPs酶可能是代谢开关的组成部分，其允许响应于营养可用性而在异生和糖酵解之间快速转换。
Allosteric activation of fructose-1,6-bisphosphatase (FBPase) from Escherichia coli by phosphoenolpyruvate implies rapid feed-forward activation of gluconeogenesis in heterotrophic bacteria. But how do such bacteria rapidly down-regulate an activated FBPase in order to avoid futile cycling? Demonstrated here is the allosteric inhibition of E. coli FBPase by glucose 6-phosphate (Glc-6-P), the first metabolite produced upon glucose transport into the cell. FBPase undergoes a quaternary transition from the canonical R-state to a T-like state in response to Glc-6-P and AMP ligation. By displacing Phe(15), AMP binds to an allosteric site comparable with that of mammalian FBPase. Relative movements in helices H1 and H2 perturb allosteric activator sites for phosphoenolpyruvate. Glc-6-P binds to allosteric sites heretofore not observed in previous structures, perturbing subunits that in pairs form complete active sites of FBPase. Glc-6-P and AMP are synergistic inhibitors of E. coli FBPase, placing AMP/Glc-6-P inhibition in bacteria as a possible evolutionary predecessor to AMP/fructose 2,6-bisphosphate inhibition in mammalian FBPases. With no exceptions, signature residues of allosteric activation appear in bacterial sequences along with key residues of the Glc-6-P site. FBPases in such organisms may be components of metabolic switches that allow rapid changeover between gluconeogenesis and glycolysis in response to nutrient availability.