The dimensions of the protein import channels in the outer and inner mitochondrial membranes

Most mitochondrial proteins are imported into mitochondria through transmembrane channels composed largely, and perhaps exclusively, of proteins. We have determined the effective internal diameter of the protein import channel in the mitochondrial outer membrane to be between 20 Å and 26 Å during translocation. The diameter of the import channel in the inner membrane is smaller than the diameter of the outer membrane import channel. These results were obtained by measuring the effect of rigid steric bulk introduced into precursor proteins on import.

绝大多数线粒体蛋白通过主要甚至完全由蛋白质构成的跨膜通道被导入线粒体中。本研究已确定，在蛋白质转运过程中，线粒体外膜（mitochondrial outer membrane）中的蛋白质导入通道（protein import channel）的有效内径介于20埃（Å）与26埃（Å）之间。线粒体内膜中的导入通道内径小于线粒体外膜导入通道的内径。上述研究结果通过检测引入至前体蛋白（precursor proteins）中的刚性立体位阻基团对蛋白质导入过程的影响而获得。