Peleg I, Kahane I, Eldor A, Groschel-Stewart U, Levy-Toledano S, Muhlrad A
Department of Membrane and Ultrastructure Research, Hebrew University-Hadassah Medical School, Jerusalem, Israel.
Thromb Res. 1989 Oct 1;56(1):1-12. doi: 10.1016/0049-3848(89)90002-9.
Our previous studies indicate that platelets contain two myosin isoforms, one of them localized in the membrane while the other in the cytoplasmic compartment. Structural and functional differences of these myosins have been characterized. In this study two platelet membrane subfractions, the external and the internal membranes, were isolated simultaneously from a crude membrane fraction and their purity was characterized using specific marker enzymes. Myosin was shown to be present in both membrane fractions and its structural and immunological properties were investigated. The electrophoretic mobilities of myosin in both membrane preparations were identical to the mobility of its cytoplasmic counterpart. Two-dimensional peptide mapping of the iodinated tryptic peptides of the myosin heavy chains indicated that at least one peptide is missing in the maps of the myosins from the external and internal membranes as compared to their soluble counterpart. Our data suggest that myosin is located in three distinct platelet compartments: cytosol, external and internal membranes. The same myosin isoform is located in the two membrane compartments, while the isoform found in the cytosol is different. The observed variations in the structure of the two isoforms may reflect differences in their respective physiological functions.
我们之前的研究表明，血小板含有两种肌球蛋白异构体，其中一种定位于膜上，另一种位于细胞质区室。这些肌球蛋白的结构和功能差异已得到表征。在本研究中，从粗膜组分中同时分离出两种血小板膜亚组分，即外膜和内膜，并使用特异性标记酶对其纯度进行了表征。结果表明，两种膜组分中均存在肌球蛋白，并对其结构和免疫学特性进行了研究。两种膜制剂中肌球蛋白的电泳迁移率与其细胞质对应物的迁移率相同。肌球蛋白重链碘化胰蛋白酶肽的二维肽图谱表明，与可溶性对应物相比，外膜和内膜肌球蛋白图谱中至少缺少一种肽。我们的数据表明，肌球蛋白位于血小板的三个不同区室：胞质溶胶、外膜和内膜。相同的肌球蛋白异构体位于两个膜区室中，而在胞质溶胶中发现的异构体则不同。观察到的两种异构体结构上的差异可能反映了它们各自生理功能的差异。
