EVIDENCE FOR A LINK BETWEEN TRANSLOCATION AND PROCESSING DURING PROTEIN IMPORT INTO SOYBEAN MITOCHONDRIA

The effect of metal chelators on protein import was investigated using isolated soybean mitochondria and soybean precursor proteins. Adding 1,10-phenanthroline, a metal chelator that can cross both mitochondria l membranes abolished import of both the alternative oxidase, and the F(A)d subunit of the ATP synthase, a matrix located protein. Other met al chelators such as EDTA, 1,7-phenanthroline and 4,7-phenanthroline, which cannot cross the mitochondrial membranes, had no effect on impor t. When processing, a known metal-dependent step inside mitochondria, was inhibited using a mutagenesis approach (changing a -2 arginine to a -2 glycine in the pre-piece of the precursor), so was import. Thus i t would appear that in soybean, at least, translocation of proteins ac ross the mitochondrial membrane, as well as processing, relies on a me tal dependent step. Taken together, the data suggest that the two proc esses may be directly connected in these mitochondria.