The mitochondrial protein import motor: Dissociation of mitochondrial hsp70 from its membrane anchor requires ATP binding rather than ATP hydrolysis

During protein import into mitochondria, matrix‐localized mitochondrial hsp70 (mhsp70) interacts with the inner membrane protein Tim44 to pull a precursor across the inner membrane. We have proposed that the Tim44‐mhsp70 complex functions as an ATP‐dependent “translocation motor” that exerts an inwa...

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Bibliographic Details
Published in:Protein science 1996-04, Vol.5 (4), p.759-767
Main Authors: Horst, Martin, Oppliger, Wolfgang, Feifel, Bastian, Schatz, Gottfried, Glick, Benjamin S.
Format: Article
Language:English
Subjects:
Adenosine Triphosphate - metabolism
Biological Transport
Carrier Proteins - metabolism
Electrophoresis, Polyacrylamide Gel
hsp70
HSP70 Heat-Shock Proteins - metabolism
Hydrolysis
Kinetics
Membrane Proteins - metabolism
mitochondria
Mitochondria - metabolism
Mitochondrial Membrane Transport Proteins
nucleotides
Protein Binding
protein transport
Saccharomyces cerevisiae
Saccharomyces cerevisiae Proteins
translocation
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Summary:During protein import into mitochondria, matrix‐localized mitochondrial hsp70 (mhsp70) interacts with the inner membrane protein Tim44 to pull a precursor across the inner membrane. We have proposed that the Tim44‐mhsp70 complex functions as an ATP‐dependent “translocation motor” that exerts an inward force on the precursor chain. To clarify the role of ATP in mhsp70‐driven translocation, we tested the effect of the purified ATP analogues AMP‐PNP and ATPγS on the Tim44‐mhsp70 interaction. Both analogues mimicked ATP by causing dissociation of mhsp70 from Tim44. ADP did not disrupt the Tim44‐mhsp70 complex, but did block the ATP‐induced dissociation of this complex. In the presence of ADP, mhsp70 can bind simultaneously to Tim44 and to a peptide substrate. These data are consistent with a model in which mhsp70 first hydrolyzes ATP, then associates tightly with Tim44 and a precursor protein, and finally undergoes a conformational change to drive translocation.
ISSN:0961-8368
1469-896X
DOI:10.1002/pro.5560050421