Electrogenic sodium-proton exchange in membrane vesicles from crab (Carcinus maenas) gill.
Electrogenic sodium-proton exchange in membrane vesicles from crab (Carcinus maenas) gill.
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蟹（Carcinus maenas）鳃膜囊泡中的电化学钠-质子交换。
DOI：
10.1152/ajpregu.1989.257.4.r924
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
Towle,DW
中科院分区：
文献类型：
--
作者：
Shetlar,RE;Towle,DW
以吖啶橙为基础的荧光测定显示，从吸收Na+的绿蟹后鳃中提取的质膜囊泡含有对氨酰（Ki = 280 μ mol/l）敏感的Na+-H+反转运蛋白。发现锂支持Li+-H+交换，产生Michaelis-Menten动力学（K0.5 = 20 mmol/l）， Hill系数为1.32 +/- 0.06，表明化学计量量为1 Li+:1 H+。然而，Na+-H+交换的化学计量似乎是2na +: 1h +。交换速率与Na+浓度呈s型关系（K0.5 = 34 mmol/l）， Hill系数为1.99 +/- 0.18。用电位敏感染料3,3'-二丙基硫二羧酸碘化进行的测量直接证明了Na+-H+交换的电原性。负载Na+的囊泡在不含Na+的介质中表现出比在含Na+的介质中更大的电位变化，而外部Na+的加入则逆转了发育的电位。阿米洛利降低了膜极化速率，消除了外部Na+的逆转。因此，甲壳动物的Na+-H+反向转运蛋白与脊椎动物的反向转运蛋白相似，但具有独特的电致性。
Plasma membrane vesicles from Na+-absorbing posterior gills of the green crab Carcinus maenas were shown to contain a Na+-H+ antiporter sensitive to amiloride (Ki = 280 mumol/l), using a fluorometric assay based on acridine orange. Lithium was found to support Li+-H+ exchange, giving Michaelis-Menten kinetics (K0.5 = 20 mmol/l) and a Hill coefficient of 1.32 +/- 0.06, indicating a stoichiometry of 1 Li+:1 H+. The stoichiometry of Na+-H+ exchange, however, appeared to be 2 Na+:1 H+. The dependence of exchange rate on Na+ concentration followed a sigmoid relationship (K0.5 = 34 mmol/l), producing a Hill coefficient of 1.99 +/- 0.18. Measurements made with the potential-sensitive dye 3,3'-dipropylthiadicarboxocyanine iodide directly demonstrated electrogenicity of Na+-H+ exchange. Na+-loaded vesicles showed greater potential change upon addition to Na+-free medium than upon addition to Na+-containing medium, and the developed potential was reversed by the addition of external Na+. Amiloride reduced the rate of membrane polarization and abolished the reversal by external Na+. The crustacean Na+-H+ antiporter therefore bears similarities to the vertebrate antiporter but is uniquely electrogenic.