大肠杆菌的蜜二糖转运
Melibiose transport of Escherichia coli.
作者信息
Tanaka K, Niiya S, Tsuchiya T
出版信息
J Bacteriol. 1980 Mar;141(3):1031-6. doi: 10.1128/jb.141.3.1031-1036.1980.
Transport of [3H]melibiose, prepared from [3H]raffinose, was investigated in Escherichia coli. Na+ stimulated the transport of melibiose via the melibiose system, whereas Li+ inhibited it. Kinetic parameters of melibiose transport were determined. The Kt values were 0.57 mM in the absence of Na+ or Li+, 0.27 mM in the presence of 10 mM NaCl, and 0.29 mM in the presence of 10 mM LiCl. The Vmax values were 40 and 46 nmol/min per mg of protein in the absence and in the presence of NaCl and 18 nmol/min per mg of protein in the presence of LiCl. Melibiose transport via the melibiose system was temperature sensitive in a wild-type strain of Escherichia coli and was not inhibited by lactose. On the other hand, melibiose uptake via the lactose system was not temperature sensitive, was inhibited by lactose, and was not affected by Na+ and Li+. Methyl-beta-D-thiogalactoside, a substrate for both systems, inhibited the transport of melibiose via both systems.
对由[³H]棉子糖制备的[³H]蜜二糖在大肠杆菌中的转运进行了研究。Na⁺通过蜜二糖系统刺激蜜二糖的转运，而Li⁺则抑制其转运。测定了蜜二糖转运的动力学参数。在不存在Na⁺或Li⁺时，Kt值为0.57 mM；在存在10 mM NaCl时，Kt值为0.27 mM；在存在10 mM LiCl时，Kt值为0.29 mM。在不存在和存在NaCl时，Vmax值分别为每毫克蛋白质40和46 nmol/min，在存在LiCl时，Vmax值为每毫克蛋白质18 nmol/min。在大肠杆菌野生型菌株中，通过蜜二糖系统的蜜二糖转运对温度敏感，且不受乳糖抑制。另一方面，通过乳糖系统的蜜二糖摄取对温度不敏感，受乳糖抑制，且不受Na⁺和Li⁺影响。两种系统的底物甲基-β-D-硫代半乳糖苷抑制了通过两种系统的蜜二糖转运。
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