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. 1996 Apr;5(4):759–767. doi: 10.1002/pro.5560050421

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

M Horst 1, W Oppliger 1, B Feifel 1, G Schatz 1, B S Glick 1
PMCID: PMC2143374  PMID: 8845766

Abstract

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 ATP gamma S 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.

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Selected References

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