Bolliger L, Junne T, Schatz G, Lithgow T
Biozentrum, Universität Basel, Switzerland.
EMBO J. 1995 Dec 15;14(24):6318-26. doi: 10.1002/j.1460-2075.1995.tb00322.x.
Mitochondrial precursor proteins made in the cytosol bind to a hetero-oligomeric protein import receptor on the mitochondrial surface and then pass through the translocation channel across the outer membrane. This translocation step is accelerated by an acidic domain of the receptor subunit Mas22p, which protrudes into the intermembrane space. This 'trans' domain of Mas22p specifically binds functional mitochondrial targeting peptides with a Kd of < 1 microM and is required to anchor the N-terminal targeting sequence of a translocation-arrested precursor in the intermembrane space. If this Mas22p domain is deleted, respiration-driven growth of the cells is compromised and import of different precursors into isolated mitochondria is inhibited 3- to 8-fold. Binding of precursors to the mitochondrial surface appears to be mediated by cytosolically exposed acidic domains of the receptor subunits Mas20p and Mas22p. Translocation of a precursor across the outer membrane thus appears to involve sequential binding of the precursor's basic and amphiphilic targeting signal to acidic receptor domains on both sides of the membrane.
在细胞质中合成的线粒体前体蛋白与线粒体表面的异源寡聚蛋白导入受体结合，然后穿过外膜上的转运通道。受体亚基Mas22p的酸性结构域加速了这一转运步骤，该结构域伸入膜间隙。Mas22p的这种“反式”结构域以小于1微摩尔的解离常数特异性结合功能性线粒体靶向肽，并且是将转运受阻前体的N端靶向序列锚定在膜间隙所必需的。如果删除该Mas22p结构域，细胞的呼吸驱动生长就会受损，不同前体导入分离线粒体的过程会被抑制3至8倍。前体与线粒体表面的结合似乎是由受体亚基Mas20p和Mas22p胞质暴露的酸性结构域介导的。因此，前体穿过外膜的转运似乎涉及前体的碱性和亲水靶向信号与膜两侧酸性受体结构域的顺序结合。
