Mancuso D, Glaser L
J Cell Physiol. 1985 Jun;123(3):297-304. doi: 10.1002/jcp.1041230302.
A previous report from this laboratory (Rothenberg et al., 1983a) demonstrated the presence of an Na+/H+ exchanger in human epidermoid carcinoma A431 cells. We now characterize surface-derived membrane vesicles from this cell line which contain a functional Na+/H+ exchanger. The Na+/H+ exchanger in A431 vesicles shares a number of characteristics in common with previously described Na+/H+ exchangers including the following: (1) Na+ uptake is stimulated by an outward-directed pH gradient and inhibited by an inward-directed pH gradient. (2) Na+ uptake is inhibited by amiloride and its analogs and their relative effectiveness is similar in vesicles and A431 cells. (3) The Na+/H+ exchanger uses Na+ or Li+ as a substrate but not K+ or Cs+. (4) H+ efflux is stimulated by an inward-directed Na+ gradient and inhibited by the amiloride analog 5-N-dimethylamiloride. The Na+/H+ exchanger in these membrane vesicles is activated allosterically by low intravesicular pH. The apparent pKa of the activating site is 6.4-6.6, characteristic of the NA+/H+ exchanger before activation by mitogens.
本实验室之前的一份报告（Rothenberg等人，1983a）证明了人表皮样癌A431细胞中存在Na+/H+交换体。我们现在对来自该细胞系的表面衍生膜泡进行了表征，这些膜泡含有功能性Na+/H+交换体。A431膜泡中的Na+/H+交换体与先前描述的Na+/H+交换体具有许多共同特征，包括以下几点：（1）向外的pH梯度刺激Na+摄取，向内的pH梯度抑制Na+摄取。（2）氨氯地平及其类似物抑制Na+摄取，它们在膜泡和A431细胞中的相对有效性相似。（3）Na+/H+交换体以Na+或Li+作为底物，但不以K+或Cs+作为底物。（4）向内的Na+梯度刺激H+外流，氨氯地平类似物5-N-二甲基氨氯地平抑制H+外流。这些膜泡中的Na+/H+交换体通过低泡内pH变构激活。激活位点的表观pKa为6.4-6.6，这是有丝分裂原激活前Na+/H+交换体的特征。
