Milanick M A, Gunn R B
Am J Physiol. 1984 Sep;247(3 Pt 1):C247-59. doi: 10.1152/ajpcell.1984.247.3.C247.
Sulfate influx into human red blood cells was measured at 0 and 22 degrees C at several fixed external pH values between 3 and 10. These cells had normal internal pH and chloride concentrations so that sulfate influx was not limited by the efflux half-cycle reactions. The flux was a Michaelis-Menten function of sulfate concentration at each pH with K1/2SO4 = 4-10 mM. External protons activated influx 100-fold at a single site with a pK = 5.9 at 22 degrees C and 5.5 at 0 degrees C. This pK is similar to the value 5.99 +/- 0.3 for external proton binding to the sulfate-loaded transporter at 0 degrees C (J. Gen. Physiol. 79: 87-114, 1982). The flux was stilbene sensitive even in valinomycin-treated cells and was independent of membrane potential. This proton-activated influx appears to be proton-sulfate cotransport. At high pH there was a proton-independent flux that was membrane potential and stilbene sensitive. This proton-insensitive flux appears to be SO4(2-)/Cl- exchange or net sulfate influx. The sulfate influx over the entire pH range may be described in terms of an equation for the sum of the influxes through these two pathways on band 3.
在0℃和22℃下，于3至10之间的几个固定外部pH值下测量了硫酸盐流入人红细胞的情况。这些细胞具有正常的内部pH值和氯离子浓度，因此硫酸盐流入不受流出半周期反应的限制。在每个pH值下，通量是硫酸盐浓度的米氏函数，K1/2SO4 = 4 - 10 mM。外部质子在一个位点激活流入100倍，在22℃时pK = 5.9，在0℃时pK = 5.5。该pK值与0℃时外部质子与负载硫酸盐的转运体结合的5.99±0.3的值相似（《普通生理学杂志》79: 87 - 114, 1982）。即使在缬氨霉素处理的细胞中，通量仍对二苯乙烯敏感，且与膜电位无关。这种质子激活的流入似乎是质子 - 硫酸盐共转运。在高pH值下，存在一种与质子无关的通量，对膜电位和二苯乙烯敏感。这种对质子不敏感的通量似乎是SO4(2 - )/Cl - 交换或净硫酸盐流入。整个pH范围内的硫酸盐流入可以用一个方程来描述，该方程表示通过带3上这两条途径的流入总和。
