Günther T, Vormann J
Institute of Molecular Biology and Biochemistry, Free University of Berlin, F.R.G.
Biochem Biophys Res Commun. 1987 Nov 13;148(3):1069-74. doi: 10.1016/s0006-291x(87)80240-1.
During net Mg2+ efflux from Mg2+-preloaded chicken erythrocytes, which occurs via Na+/Mg2+ antiport, 28Mg2+ is taken up intracellularly. Km of 28Mg2+ influx amounted to 1 mM. In Na+-free medium Vmax of 28Mg2+ influx was increased and Km was reduced to 0.2 mM. 28Mg2+ influx was noncompetitively inhibited by amiloride as was found for Na+/Mg2+ antiport. The results indicate that, extracellularly, Mg2+ can compete with Na+ for common binding sites of the Na+/Mg2+ antiporter, resulting in 28Mg2+-24Mg2+ exchange. The rate of Mg2+ exchange depends on extracellular Na+ and on the rate of net Mg2+ efflux.
在通过钠/镁反向转运体从预先加载镁离子的鸡红细胞中净流出镁离子的过程中，28镁离子被细胞内摄取。28镁离子流入的米氏常数为1毫摩尔。在无钠培养基中，28镁离子流入的最大反应速度增加，米氏常数降至0.2毫摩尔。如钠/镁反向转运体的情况一样，28镁离子流入受到氨氯吡脒的非竞争性抑制。结果表明，在细胞外，镁离子可与钠离子竞争钠/镁反向转运体的共同结合位点，从而导致28镁离子 - 24镁离子交换。镁离子交换速率取决于细胞外钠离子和净镁离子流出速率。
