THE SACCHAROMYCES-CEREVISIAE MTS1 GENE ENCODES A PUTATIVE RNA-BINDINGPROTEIN INVOLVED IN MITOCHONDRIAL PROTEIN TARGETING

Most proteins present in the mitochondrion are nuclear encoded, and ar e directed to the organelle by virtue of a targeting sequence at the N terminus of the precursor protein. Mitochondrial (mt) protein targeti ng appears to require several accessory proteins that recognise mt pre cursors both in the cytoplasm and at the mt surface. We describe here the use of yeast genetics to identify a protein that is required for m t protein targeting. Two yeast mutants (mts1 and mts2) were isolated a s extragenic suppressors of a known targeting defect in the presequenc e of the beta-subunit of ATP synthase. We have cloned and sequenced th e wild-type allele of one of these genes (MTS1) and shown that it enco des a member of a family of RNA-binding proteins that is essential for growth.