Kirchhausen T, Staunton D E, Springer T A
Center for Blood Research, Department of Anatomy and Cellular Biology, Harvard Medical School, Boston, MA 02115.
J Leukoc Biol. 1993 Mar;53(3):342-6. doi: 10.1002/jlb.53.3.342.
Intercellular adhesion molecule 1 (ICAM-1), a member of the immunoglobulin gene superfamily, is a cell surface glycoprotein with an extracellular domain comprising five immunoglobulin-like domains. Soluble ICAM-1, a recombinant protein truncated at the transmembrane domain, has a rod-like shape, 19 nm long overall, with a characteristic bend 7.6 nm from one end of the molecule. Because the link between domain D2 and domain D3 is proline rich, it has been proposed that the short arm contains domains D1 and D2 and the long arm contains domains D3-D5. We used single-molecule electron microscopy of soluble ICAM-1 decorated with monoclonal antibodies specific for domains D1 and D4 to show that the bend instead lies between domains D3 and D4. Therefore, the short arm lies closer to the plasma membrane, whereas the long arm, containing all the known ligand binding sites on ICAM-1, is positioned toward the target cell surface.
细胞间黏附分子1（ICAM-1）是免疫球蛋白基因超家族的成员，是一种细胞表面糖蛋白，其细胞外结构域包含五个免疫球蛋白样结构域。可溶性ICAM-1是一种在跨膜结构域处截短的重组蛋白，呈棒状，全长19纳米，在距分子一端7.6纳米处有一个特征性弯曲。由于结构域D2和结构域D3之间的连接富含脯氨酸，有人提出短臂包含结构域D1和D2，长臂包含结构域D3-D5。我们使用用针对结构域D1和D4的单克隆抗体修饰的可溶性ICAM-1的单分子电子显微镜来表明，弯曲实际上位于结构域D3和D4之间。因此，短臂更靠近质膜，而包含ICAM-1上所有已知配体结合位点的长臂则朝向靶细胞表面。
