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

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.
Mesh Terms:
Adenosine Triphosphatases, Carrier Proteins, HSP70 Heat-Shock Proteins, Membrane Transport Proteins, Mitochondrial Membrane Transport Proteins, Molecular Chaperones, Molecular Motor Proteins, Protein Transport, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins
Nat Commun
Date: Jul. 10, 2014
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