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首页> 外文期刊>Journal of bacteriology >Osmotic and Chill Activation of Glycine Betaine Porter II in Listeria monocytogenes Membrane Vesicles
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Osmotic and Chill Activation of Glycine Betaine Porter II in Listeria monocytogenes Membrane Vesicles

机译：单核细胞增生李斯特菌膜囊泡中甘氨酸甜菜碱Porter II的渗透和冷活化

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Listeria monocytogenes is a foodborne pathogen known for its tolerance to conditions of osmotic and chill stress. Accumulation of glycine betaine has been found to be important in the organism's tolerance to both of these stresses. A procedure was developed for the purification of membranes from L. monocytogenes cells in which the putative ATP-driven glycine betaine permease glycine betaine porter II (Gbu) is functional. As is the case for the L. monocytogenes sodium-driven glycine betaine uptake system (glycine betaine porter I), uptake in this vesicle system was dependent on energization by ascorbate-phenazine methosulfate. Vesicles lacking the gbu gene product had no uptake activity. Transport by this porter did not require sodium ion and could be driven only weakly by artificial gradients. Uptake rates could be manipulated under conditions not affecting secondary transport but known to affect ATPase activity. The system was shown to be both osmotically activated and cryoactivated. Under conditions of osmotic activation, the system exhibited Arrhenius-type behavior although the uptake rates were profoundly affected by the physical state of the membrane, with breaks in Arrhenius curves at approximately 10 and 18°C. In the absence of osmotic activation, the permease could be activated by decreasing temperature within the range of 15 to 4°C. Kinetic analyses of the permease at 30°C revealedKm values for glycine betaine of 1.2 and 2.9 μM with V max values of 2,200 and 3,700 pmol/min · mg of protein under conditions of optimal osmotic activation as mediated by KCl and sucrose, respectively.
机译：单核细胞增生李斯特菌是一种食源性病原体，以其对渗透压和寒冷胁迫的耐受性而闻名。已经发现甘氨酸甜菜碱的积累对于生物体对这两种压力的耐受性都很重要。开发了从 L纯化膜的程序。单核细胞增生细胞，其中推测的ATP驱动的甘氨酸甜菜碱通透酶甘氨酸甜菜碱转运蛋白II（Gbu）起作用。与 L一样。单核细胞增生素钠驱动的甘氨酸甜菜碱摄取系统（甘氨酸甜菜碱搬运剂I），该囊泡系统的摄取取决于抗坏血酸-吩嗪甲硫酸盐的增能作用。缺乏 gbu 基因产物的囊泡没有吸收活性。该搬运工的运输不需要钠离子，只能通过人工梯度弱驱动。可以在不影响二级转运但已知会影响ATPase活性的条件下控制摄取速率。该系统显示为渗透激活和低温激活。在渗透激活的条件下，该系统表现出Arrhenius型行为，尽管吸收速率受膜的物理状态影响很大，在大约10和18°C时Arrhenius曲线断裂。在没有渗透活化的情况下，可以通过降低15至4℃范围内的温度来活化通透酶。在30°C下进行的渗透酶动力学分析表明， V max 的甘氨酸甜菜碱的 K m 值为1.2和2.9μM。在KCl和蔗糖介导的最佳渗透活化条件下，蛋白质的sub>值分别为2,200 pmol / min和3,700 pmol / min·mg。

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