CHARACTERIZATION OF THE PREPROTEIN TRANSLOCASE OF THE OUTER MITOCHONDRIAL-MEMBRANE BY BLUE NATIVE ELECTROPHORESIS

The mitochondrial outer membrane contains import receptors for nuclear -encoded preproteins and a general import pore responsible for membran e translocation of preproteins. Receptors and the general import pore have been suggested to assemble into a loose complex. However, biochem ical characterization of the complex has been limited so far. We repor t that blue native electrophoresis separates two complexes. One comple x of similar to 400 kDa contains the receptor Tom22 and the general im port pore component Tom40, the other complex of similar to 120 kDa con tains the receptor Tom70. A preprotein accumulated at the general impo rt pore apparently co-migrates with the larger complex, suggesting the functionality of the complex. We conclude that the translocase of the outer membrane consists of at least two subcomplexes and that blue na tive electrophoresis will be a powerful tool for biochemical analysis of the complexes.