IMPORT OF TRANSCRIPTION FACTOR MTF1 INTO THE YEAST MITOCHONDRIA TAKESPLACE THROUGH AN UNUSUAL PATHWAY

We report studies of the import into mitochondria of MTF1, a nucleus-e ncoded factor that markedly stimulates the specific transcription of m itochondrial DNA. Unlike most of the mitochondrial precursor proteins studied so far, import of MTF1 does not appear to require a receptor o n the outer membrane, membrane potential across the inner membrane, or ATP hydrolysis. Its import is not affected by low temperature. It lac ks a cleavable presequence but translocates across the inner membrane through its amino terminus; its sorting is independent of hsp60. Our r esults indicate an unusual and distinct import pathway for MTF1 into t he yeast mitochondria.