Schekman R, Singer S J
Proc Natl Acad Sci U S A. 1976 Nov;73(11):4075-9. doi: 10.1073/pnas.73.11.4075.
Concanavalin A (Con A) is taken up by endocytosis in mature erythrocytes of newborn humans but not in adult red cells. Thin sections of neonatal cells incubated with ferritin-conjugated Con A at 37 degrees show ferritin clusters on invaginations at the surface and in intracellular vesicles, but such invaginations and vesicles are absent with adult cells. The endocytosis induced by ferritin-conjugated Con A is inhibited at 0 degrees, and by methyl-alpha-D-mannopyranoside at 37 degrees. Succinylation of Con A, which is known to convert it from the tetrameric to dimeric form, renders Con A inactive in cell agglutination and endocytotic vesicle formation, presumably by reducing the number of oligosaccharide chains simultaneously bound by a single Con A molecule. Ferritin-conjugated succinyl Con A binds to neonatal erythrocytes but does not induce endocytosis; if, however, antibodies to ferritin are now added, endocytosis occurs. These results are consistent with a greater lateral mobility of at least a fraction of Con A recptors in the membrane of the intact neonatal erythrocyte compared to the adult. The results also support the hypothesis that the clustering of receptors is obligatory for endocytosis to occur. No discernible difference was found in the sodium dodecyl sulfate/polyacrylamide gel patterns of the membrane proteins of the neonatal and adult cells.
伴刀豆球蛋白A（Con A）可被新生儿成熟红细胞通过内吞作用摄取，但成年红细胞则不能。在37摄氏度下用铁蛋白偶联的Con A孵育新生儿细胞的薄片，可见铁蛋白簇出现在细胞表面的内陷处和细胞内小泡中，但成年细胞没有这种内陷和小泡。铁蛋白偶联的Con A诱导的内吞作用在0摄氏度时受到抑制，在37摄氏度时受到甲基-α-D-甘露糖苷的抑制。已知Con A琥珀酰化会使其从四聚体形式转变为二聚体形式，这使得Con A在细胞凝集和内吞小泡形成中失去活性，推测是通过减少单个Con A分子同时结合的寡糖链数量。铁蛋白偶联的琥珀酰Con A与新生儿红细胞结合但不诱导内吞作用；然而，如果现在加入抗铁蛋白抗体，就会发生内吞作用。这些结果与完整的新生儿红细胞膜中至少一部分Con A受体的侧向流动性比成年红细胞更大是一致的。这些结果也支持了这样的假说，即受体的聚集是内吞作用发生所必需的。在新生儿和成年细胞的膜蛋白的十二烷基硫酸钠/聚丙烯酰胺凝胶图谱中未发现明显差异。
