Precursor proteins in transit through mitochondrial contact sites interact with hsp70 in the matrix.
We previously reported that hsp70 in the mitochondrial matrix (mt-hsp 70 = Ssclp) is required for import of precursor proteins destined for the matrix or intermembrane space. Here we show that mt-hsp70 is also needed for the import of mitochondrial inner membrane proteins. In particular, the precursor of ADP/ATP carrier that is known not to interact with hsp60 on its assembly pathway requires functional mt-hsp70 for import, suggesting a general role of mt-hsp70 in membrane translocation of precursors. Moreover, a precursor arrested in contact sites was specifically co-precipitated with antibodies directed against mt-hsp70. We conclude that mt-hsp70 is directly involved in the translocation of many, if not all, precursor proteins that are transported across the inner membrane.
Ostermann
J
J
Institut für Physiologische Chemie, Universität München, Germany.
Voos
W
W
Kang
P J
PJ
Craig
E A
EA
Neupert
W
W
Pfanner
N
N
D001692:Biological Transport; D002451:Cell Compartmentation; D003575:Cytochromes c1 / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism*; D007425:Intracellular Membranes / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D000226:Mitochondrial ADP, ATP Translocases / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism; D012441:Saccharomyces cerevisiae; D013762:Tetrahydrofolate Dehydrogenase / Q000378:metabolism
D005656:Fungal Proteins; D006360:Heat-Shock Proteins; D008565:Membrane Proteins; D011498:Protein Precursors; D003575:Cytochromes c1; D000226:Mitochondrial ADP, ATP Translocases; D013762:Tetrahydrofolate Dehydrogenase