DISSOCIATION OF IMPORT OF THE RIESKE IRON-SULFUR PROTEIN INTO SACCHAROMYCES-CEREVISIAE MITOCHONDRIA FROM PROTEOLYTIC PROCESSING OF THE PRESEQUENCE

The correlation between the import of the Rieske iron-sulfur protein i nto the mitochondrial matrix and processing of the precursor protein b y matrix processing peptidase was investigated using high concentratio ns of metal chelators and iron sulfur protein in which the recognition site for the matrix processing peptidase was destroyed by site-direct ed mutagenesis. High concentrations of EDTA and o-phenanthroline inhib it import of iron-sulfur protein into the matrix. The non-chelating st ructural isomers m-phenanthroline and p-phenan-throline inhibit import similar to o-phenanthroline, indicating that inhibition of import is mainly independent of the metal chelating ability of the compounds. Ir on-sulfur protein in which the recognition site for the matrix process ing peptidase had been destroyed by a point mutation was efficiently i mported into the matrix space. Import of this mutant iron-sulfur prote in was inhibited by the same concentrations of EDTA and o-phenanthroli ne which inhibit import of the wild-type protein. These results indica te that import of the iron-sulfur protein into the mitochondrial matri x is independent of proteolytic processing of the presequence, and tha t o-phenanthroline together with EDTA inhibits import of iron-sulfur p rotein into the matrix space of mitochondria by inhibiting a step othe r than proteolysis of the presequence.