2-Deoxyglucose Kills Myxococcus Xanthus

尤德里安捕食性革兰氏阴性细菌，黄色粘球菌，其代谢能量主要来自氨基酸的氧化。这一物种是粘细菌的最好的代表，粘细菌是唯一一类通过经历多细胞发育程序来应对饥饿(蛋白质)的细菌。此前的研究表明，黄花莲并不“爱吃甜食”。也就是说，包括葡萄糖在内的简单己糖不会刺激其生长，即使在特定的培养基上也是如此。然而，黄曲霉对葡萄糖类似物2-脱氧葡萄糖(2dGIc)很敏感。这种抗生素是有毒的，因为它被己糖激酶磷酸化，己糖激酶是糖分解代谢的初级糖酵解途径中的第一种酶，存在于大多数利用葡萄糖的生物体中。对黄曲霉抗2dGIc自发突变体的分离和鉴定表明，黄曲霉产生己糖激酶，必须运输单糖。这种己糖激酶是不寻常的，因为它被氨基葡萄糖和N-乙酰氨基葡萄糖这两种基本的己糖胺所抑制。另一种细菌己糖激酶，由E.coil制造，也被相同的糖抑制。这项研究的三个主要目标是：(1)了解为什么这些酶对2dGIc敏感，并被己糖胺抑制；(2)确定2dGIc-6-磷酸在大多数生物体中负责2dGIc毒性的确切靶点；(3)了解该生物体中控制氨基酸优先于葡萄糖的调控机制。为了完成第一项任务，将使用动力学和机械方法研究己糖激酶与底物结合和利用这些糖的动力学。黄曲霉的己糖激酶基因将被克隆和测序，黄曲霉和E.cos的酶都将得到纯化。其次，最近发现，细胞内2dGIc-6-磷酸的产生导致黄色微囊藻中ATP的耗尽，就像在哺乳动物细胞中所做的那样，这导致了对参与中央碳代谢的关键酶的研究，这种关键酶被低浓度的2dGIc-6-磷酸特异性地抑制，同样是使用传统的生化策略。第三，绿色分枝杆菌的葡萄糖分解代谢很容易氧化葡萄糖，黄色分枝杆菌的葡萄糖分解代谢可能不会。许多生物，如人类，燃烧糖来获取能量，但更喜欢富含蛋白质的饮食。土壤细菌，黄色粘球菌，极端地选择富含蛋白质的饮食(牛排)，而不是富含碳水化合物的饮食(土豆)，因为糖不会刺激它的生长。这项研究的目的是了解为什么一些个体有机体有这种饮食偏好。生化研究表明，爱吃牛排的黄色分枝杆菌仍然能尝到糖的味道，因为它被2-脱氧葡萄糖的甜味毒素愚弄了，这种毒素尝起来像富含葡萄糖的甜味剂佳得乐TM，但效果正好相反。这种毒素，2-脱氧葡萄糖，50年来一直被认为对大多数生物是有毒的。除了发现它会消耗许多活细胞中的ATP(能量)水平之外，没有人真正理解其中的原因，包括黄花莲。黄花假单胞菌将被用作模式生物，以弄清楚这种毒素为什么是一种毒物，同时，在基本化学水平上获得关于有机体如何选择食物的基本见解。

YouderianThe predatory Gram-negative bacterium, Myxococcus xanthus, derives its metabolic energy primarily from the oxidation of amino acids. This species is the best-characterized representative of the Myxobacteria, the only group of bacteria that respond to starvation (for proteins) by undergoing a program of multicellular development. Previous studies suggested that M. xanthus does not have a "sweet tooth". That is, simple hexose sugars including glucose do not stimulate its growth, even on defined medium. However, M. xanthus is sensitive to the glucose analogue, 2-deoxyglucose (2dGIc). This antibiotic is toxic, because it is phosphorylated by hexokinase, the first enzyme in the primary glycolytic pathway for sugar catabolism present in most organisms that utilize glucose. The isolation and characterization of spontaneous mutants of M. xanthus resistant to 2dGIc shows that M. xanthus makes a hexokinase and must transport simple sugars. This hexokinase is unusual, because it is inhibited by the two essential hexosamine sugars glucosamine and N-acetylglucosamine. Another bacterial hexokinase, made by E. coil, is also inhibited by the same sugars. The three main goals of this research are: (1) to understand why these enzymes are sensitive to 2dGIc and inhibited by hexosamines; (2), to identify the precise target of 2dGIc-6-phosphate responsible for the toxicity of 2dGIc in most organisms; and (3) to understand the regulatory mechanism in this organism that governs the preference for amino acids over glucose. To accomplish the first task, the kinetics of substrate binding and utilization of these sugars by hexokinase will be examined using kinetic and mechanistic approaches. The hexokinase gene from M. xanthus will be cloned and sequenced, and both the M. xanthus and E. coil enzymes will be purified. Second, the recent discovery that the production of intracellular 2dGIc-6-phosphate results in the depletion of ATP in M. xanthus, as it does in mammalian cells, has led to the search for the critical enzyme involved in central carbon metabolism specifically inhibited by low concentrations of 2dGIc-6-phosphate, again using traditional biochemical tactics. Third, glucose catabolism in M. virescens, which oxidizes glucose readily, and in M. xanthus, which may not, will be compared.Many living organisms, like humans, burn sugars for energy, but prefer a rich protein diet. The soil bacterium, Myxococcus xanthus, chooses a protein-rich diet ("steak") over a carbohydrate-rich diet ("potatoes") to an extreme, because sugar doesn't stimulate its growth. The goal of this research is to understand why some individual organisms have this kind of dietary preference. Biochemical studies show that the steak-loving bacterium M. xanthus can still taste sugars, because it is fooled by the sweet poison of 2-deoxyglucose, which tastes like sweet glucose-rich Gatorade TM, but has the opposite effect. This poison, 2-deoxyglucose, has been known to be toxic to most living things for 50 years. No one really understands why, except for the finding that it drains ATP (energy) levels in many living cells, including M. xanthus. M. xanthus will be used as a model organism to figure out why this poison is a poison, and, at the same time, gain fundamental insights at a basic chemical level about how organisms choose what to eat.