Akeson M A, Munns D N, Burau R G
Department of Land, Air, and Water Resources, University of California, Davis 95616.
Biochim Biophys Acta. 1989 Nov 17;986(1):33-40. doi: 10.1016/0005-2736(89)90269-1.
Aluminum toxicity to soil and aquatic organisms is widespread, but the mechanisms of toxicity are unknown. To understand these mechanisms, it is important to know how aluminum reacts with cell surfaces. In this report, we studied adsorption of Al3+ to liposomes composed of phosphatidylcholine, the most abundant phospholipid in plasma membranes of eukaryotic cells. Our equilibrium dialysis and electrophoresis experiments both showed that Al3+ has a 560-fold higher affinity for the phosphatidylcholine surface than Ca2+. Unlike previous reports for adsorption of divalent metals, adsorption of Al3+ to phosphatidylcholine was predicted only approximately by the Stern model. Adsorption of AlF2+ and AlF2+ to the surface was not detectable at the activities we used. From our data, we calculate that Al3+ at 5 x 10(-6) activity could neutralize the surface charge on plant cell plasma membranes and cause a surface potential shift from -30 to +11 mV. This is consistent with non-specific Al3+ inhibition of cation uptake by root cells. Al3+ adsorption to phosphatidylcholine may also play a role in aluminum uptake into cytoplasm by endocytosis.
铝对土壤和水生生物的毒性广泛存在，但毒性机制尚不清楚。为了解这些机制，了解铝与细胞表面的反应方式很重要。在本报告中，我们研究了Al3+对由磷脂酰胆碱组成的脂质体的吸附情况，磷脂酰胆碱是真核细胞膜中最丰富的磷脂。我们的平衡透析和电泳实验均表明，Al3+对磷脂酰胆碱表面的亲和力比Ca2+高560倍。与先前关于二价金属吸附的报道不同，Al3+对磷脂酰胆碱的吸附仅由斯特恩模型大致预测。在我们使用的活性条件下，未检测到AlF2+和AlF2+对表面的吸附。根据我们的数据，我们计算出活性为5×10(-6)的Al3+可以中和植物细胞质膜上的表面电荷，并使表面电位从-30 mV转变为+11 mV。这与Al3+对根细胞阳离子吸收的非特异性抑制作用一致。Al3+对磷脂酰胆碱的吸附也可能在内吞作用将铝吸收到细胞质中发挥作用。
