Import of ADP/ATP carrier into mitochondria: two receptors act in parallel

Abstract. We have identified the yeast homologue of Neurospora crassa MOM72, the mitochondrial import receptor for the ADP/ATP carrier (AAC), by func-tional studies and by eDNA sequencing. Mitochondria of a yeast mutant in which the gene for MOM72 was disrupted were impaired in specific binding and import of AAC. Unexpectedly, we found a residual, yet significant import of AAC into mitochondria l cking MOM72 that occurred via the receptor MOM19. We conclude that both MOM72 and MOM19 can direct AAC into mitochondria, lbeit with different efficiency. Moreover, the precursor of MOM72 appar-ently does not require a positively charged sequence at the extreme amino terminus for targeting to mito-chondria. A essential step in the biogenesis of cell organelles is the specific import of cytosolically synthesized precursor proteins (Wickner and Lodish, 1985