线粒体膜间隙蛋白的转运机制

线粒体约含有1 000种左右的蛋白质,其中98%以上由核基因编码,在胞质核糖体上以前体形式合成之后再转运至线粒体,并通过各种分选机制定位至线粒体的各部分。线粒体膜间隙(interm embranespace,IMS)蛋白全部在细胞质中合成,这部分蛋白的转运机制与线粒体其他部分蛋白的转运相比有其特殊性。依据转运机制和能量来源不同可以将其分为3类:Ⅰ类蛋白含有一段双组份分选信号;Ⅱ类蛋白需要膜间隙的辅助因子协同折叠;Ⅲ类蛋白含有与膜相互作用的疏水面。

Mechanisms of IMS Proteins Transport

There are more than 1000 proteins in the mitochondria,of which 98% are encoded by nuclear gene and synthesized in the cytosol and then transported into the mitochondria.All proteins of the intermembrane space(IMS) of mitochondria are synthesized in the cytosol.The mechanisms by which these polypeptides are transported into the IMS are strikingly different from other protein-translocation processes in the cell.IMS proteins reach their destination by three alternative approach that differ in the energy sources employed to drive the translocation reactions.The first class of proteins uses both hydrolysis of matrix ATP and the electrochemical potential in the inner membrane.The second class depends on the energy gain of protein folding,and the third class on the association of the proteins to high-affinity binding sites in the IMS.