HOMOLOGOUS AND HETEROLOGOUS PROTEIN IMPORT INTO MITOCHONDRIA ISOLATEDFROM THE GREEN-ALGA CHLAMYDOMONAS-REINHARDTII

We have established a homologous system for studying mitochondrial pro tein import in Chlamydomonas reinhardtii, using C. reinhardtii precurs or proteins and mitochondria isolated from C. reinhardtii. The precurs ors of the F-1 alpha ATP synthase subunit and the Rieske FeS protein w ere imported into mitochondria with high efficiency, while the F-1 bet a subunit precursor was imported with much lower efficiency. The impor t of heterologous precursor proteins from higher plants was also less efficient. The precursor of the C. reinhardtii PsaF chloroplast protei n was converted into a protease-protected form upon incubation with mi tochondria. In vitro processing studies revealed that in contrast to t he situation in higher plants, the processing of the precursors was ca talysed by a soluble, matrix-located peptidase.