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Nat Commun. 2014 Jul 10;5:4349. doi: 10.1038/ncomms5349.

Remodelling of the active presequence translocase drives motor-dependent mitochondrial protein translocation.

Author information

1
Department of Cellular Biochemistry, University Medical Center Göttingen, D-37073 Göttingen, Germany.
2
1] Department of Cellular Biochemistry, University Medical Center Göttingen, D-37073 Göttingen, Germany [2] Max Planck Institute for Biophysical Chemistry, D-37077 Göttingen, Germany.

Abstract

Proteins with N-terminal targeting signals are transported across the inner mitochondrial membrane by the presequence translocase. To drive precursor translocation, the Hsp70-import motor associates with the protein-conducting channel of the TIM23 complex. It is unknown how the ATPase cycle of Hsp70 is regulated in the context of a translocating polypeptide chain. Here we establish an assay to monitor protein dynamics in the precursor-occupied presequence translocase and find that regulatory subunits of the import motor, such as the ATPase-stimulating J-protein Pam18, are recruited into the translocation intermediate. The presence of all Hsp70 co-chaperones at the import channel is not sufficient to promote matrix protein import, instead a recharging of the active translocase with Pam18 is required for motor activity. Thus, a replenishment cycle of co-chaperones at the TIM23 complex is an integral part of Hsp70's ATPase cycle at the channel exit site and essential to maintain motor-driven mitochondrial protein import.

PMID:
25008211
DOI:
10.1038/ncomms5349
[Indexed for MEDLINE]

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