Recruitment of cytosolic J-proteins by TOM receptors promotes mitochondrial protein biogenesis
Opaliński Ł, Song J, Priesnitz C, Wenz LS, Oeljeklaus S, Warscheid B, Pfanner N, Becker T.
Mitochondrial biogenesis and functions depend on the import of about 1000 proteins that are produced as precursors on cytosolic ribosomes. Cytosolic chaperones like Hsp70 and their co-factors, the J-proteins, are involved in the transfer of precursor proteins to the mitochondrial surface. The translocase of the mitochondrial outer membrane (TOM complex) forms the general entry gate for most mitochondrial proteins. After passage of the TOM channel different protein translocases sort the precursor proteins to their final destination. While protein sorting within mitochondria is well understood, little is known how precursor proteins are delivered to the TOM complex. We report here that the J-protein Xdj1 binds specifically to the Tom22 receptor. Xdj1 guide preproteins to the Tom22 receptor to promote their import into mitochondria. In addition, we found that another cytosolic J-protein Djp1 interacts with the Tom70 receptor. Our findings indicate that cytosolic J-proteins bind to distinct TOM receptors to promote import of mitochondrial precursor proteins.