Hirayama B, Wright E M
Biochim Biophys Acta. 1984 Aug 8;775(1):17-21. doi: 10.1016/0005-2736(84)90229-3.
We have investigated the symmetry of Na+-succinate cotransport in rabbit renal brush-border membrane vesicles. Succinate influx and efflux kinetics were measured under voltage-clamped conditions using [14C]succinate and a rapid filtration procedure. Both influx and efflux were Na+-dependent, saturable, temperature-sensitive, and influenced by the trans Na+ and succinate concentrations. The system was judged to be asymmetric, since the maximal velocity for influx was 3-fold higher than that for efflux, and trans Na+ inhibited influx more than efflux. This may be due to the asymmetrical insertion of the transporter in the brush-border membrane, which leads to differences in either the forward and backward translocation rates of the fully loaded carrier or the Na+ and succinate binding constants at the inner and outer faces of the membrane.
我们研究了兔肾刷状缘膜囊泡中琥珀酸钠-钠离子共转运的对称性。在电压钳制条件下，使用[14C]琥珀酸钠和快速过滤程序测量琥珀酸盐的流入和流出动力学。流入和流出均依赖于钠离子，具有饱和性、温度敏感性，并受跨膜钠离子和琥珀酸盐浓度的影响。该系统被判定为不对称，因为流入的最大速度比流出高3倍，并且跨膜钠离子对流入的抑制作用大于对流出的抑制作用。这可能是由于转运体在刷状缘膜中的不对称插入，这导致了完全负载载体的正向和反向转运速率不同，或者膜内外表面的钠离子和琥珀酸盐结合常数不同。
