Antifolding activity of hsp60 couples protein import into the mitochondrial matrix with export to the intermembrane space

@article{Koll1992AntifoldingAO,
  title={Antifolding activity of hsp60 couples protein import into the mitochondrial matrix with export to the intermembrane space},
  author={Hans Koll and Bernard Guiard and Joachim Rassow and Joachim Ostermann and Arthur L. Horwich and Walter Neupert and F. Ulrich Hartl},
  journal={Cell},
  year={1992},
  volume={68},
  pages={1163-1175}
}
Cytochrome b2 reaches the intermembrane space of mitochondria by transport into the matrix followed by export across the inner membrane. While in the matrix, the protein interacts with hsp60, which arrests its folding prior to export. The bacterial-type export sequence in pre-cytochrome b2 functions by inhibiting the ATP-dependent release of the protein from hsp60. Release for export apparently requires, in addition to ATP, the interaction of the signal sequence with a component of the export… Expand
The sorting signal of cytochrome b2 promotes early divergence from the general mitochondrial import pathway and restricts the unfoldase activity of matrix Hsp70.
TLDR
The results indicate that the sorting signal interacts with component(s) of the inner membrane/intermembrane space during the initial import step and promotes an early divergence of b2 preproteins from the general matrix import pathway, precluding an unfolding role for mt‐Hsp70 in the translocation of most of the mature portions of a preprotein. Expand
The Sorting Route of Cytochrome b 2Branches from the General Mitochondrial Import Pathway at the Preprotein Translocase of the Inner Membrane*
TLDR
Upon import in vivo, the sorting signal of cytochromeb 2 causes an early divergence from the general matrix import pathway and thereby prevents translocation of a folded C-terminal domain into mitochondria. Expand
The requirement of matrix ATP for the import of precursor proteins into the mitochondrial matrix and intermembrane space.
TLDR
The role of ATP in the matrix for the import of precursor proteins into the various mitochondrial subcompartments was investigated by studying protein translocation at experimentally defined ATP levels and suggests that unfolding on the mitochondrial surface of tightly folded segments of preproteins is facilitated by matrix-ATP/mt-Hsp70. Expand
GTP Hydrolysis Is Essential for Protein Import into the Mitochondrial Matrix*
TLDR
GTP stimulates protein import into the matrix and the stimulatory effect is directly mediated by GTP hydrolysis and does not result from conversion of GTP to ATP, suggesting a “push-pull” mechanism of import, which may be common to other post-translational translocation pathways. Expand
The Mitochondrial Import Machinery for Preproteins
TLDR
A new era is approaching in which elaborated techniques have already allowed and will enable us to gather information about the TOM and TIM complexes on an ultrastructural level. Expand
Import of cytochrome b2 to the mitochondrial intermembrane space: The tightly folded heme‐binding domain makes import dependent upon matrix ATP
TLDR
Results indicate that cytochrome b2 reaches the intermembrane space without completely crossing the inner membrane, and some precursors fold outside the mitochondria but remain translocation‐competent, and import of these precursor in vitro does not require ATP‐dependent cytosolic chaperone proteins. Expand
Export of Proteins from Mitochondria
TLDR
This chapter discusses the protein export, and its relationship(s) to the other transport pathways of mitochondria, and several lines of evidence indicate that mitochondrially-encoded proteins are inserted into the inner mitochondrial membrane co-translationally. Expand
The ClpB Homolog Hsp78 Is Required for the Efficient Degradation of Proteins in the Mitochondrial Matrix*
TLDR
It is concluded that Hsp78 is a genuine component of the mitochondrial proteolysis system required for the efficient degradation of substrate proteins in the matrix. Expand
Protein Import by the Mitochondrial Presequence Translocase in the Absence of a Membrane Potential.
TLDR
It is reported that subunit e of the F1Fo-ATP synthase, a small single-spanning inner membrane protein that is critical for inner membrane organization, is imported by TIM23 in a process that does not require activation by the membrane potential. Expand
Energetics of Mitochondrial Protein Import and Intramitochondrial Protein Sorting
TLDR
This chapter discusses the energetics of mitochondrial protein import and intramitochon drlal protein sorting and suggests that ATP is essential for protein import into the matrix and that some precursors also need ATP outside the inner membrane. Expand
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