Palmisano A, Zara V, Hönlinger A, Vozza A, Dekker P J, Pfanner N, Palmieri F
Dipartimento Farmaco-Biologico, Università di Bari, Via E. Orabona 4, I-70125 Bari, Italy.
Biochem J. 1998 Jul 1;333 ( Pt 1)(Pt 1):151-8. doi: 10.1042/bj3330151.
We have studied the targeting and assembly of the 2-oxoglutarate carrier (OGC), an integral inner-membrane protein of mitochondria. The precursor of OGC, synthesized without a cleavable presequence, is transported into mitochondria in an ATP- and membrane potential-dependent manner. Import of the mammalian OGC occurs efficiently into both mammalian and yeast mitochondria. Targeting of OGC reveals a clear dependence on the mitochondrial surface receptor Tom70 (the 70 kDa subunit of the translocase of the outer mitochondrial membrane), whereas a cleavable preprotein depends on Tom20 (the 20 kDa subunit), supporting a model of specificity differences of the receptors and the existence of distinct targeting pathways to mitochondria. The assembly of minute amounts of OGC imported in vitro to the dimeric form can be monitored by blue native electrophoresis of digitonin-lysed mitochondria. The assembly of mammalian OGC and fungal ADP/ATP carrier occurs with high efficiency in both mammalian and yeast mitochondria. These findings indicate a dynamic behaviour of the carrier dimers in the mitochondrial inner membrane and suggest a high conservation of the assembly reactions from mammals to fungi.
我们研究了2-氧代戊二酸载体（OGC）的靶向和组装，OGC是线粒体内膜的一种整合蛋白。OGC的前体在合成时没有可裂解的前导序列，它以ATP和膜电位依赖的方式转运到线粒体中。哺乳动物OGC可有效地导入哺乳动物和酵母线粒体中。OGC的靶向显示出对线粒体表面受体Tom70（外线粒体膜转位酶的70 kDa亚基）有明显依赖性，而可裂解的前体蛋白则依赖于Tom20（20 kDa亚基），这支持了受体特异性差异的模型以及存在不同的线粒体靶向途径。通过对洋地黄皂苷裂解的线粒体进行蓝色非变性电泳，可以监测体外导入的微量OGC组装成二聚体的情况。哺乳动物OGC和真菌ADP/ATP载体在哺乳动物和酵母线粒体中都能高效组装。这些发现表明载体二聚体在线粒体内膜中具有动态行为，并提示从哺乳动物到真菌，组装反应具有高度保守性。
