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Structural basis of functional cooperation of Tim15/Zim17 with yeast mitochondrial Hsp70

Takaki Momose1, Chié Ohshima, Masahiro Maeda

  • 1Department of Chemistry, Graduate School of Science, Nagoya University, Japan.

EMBO Reports
|June 16, 2007
PubMed

Insights

Mitochondrial heat-shock protein 70 (mtHsp70) partner Tim15

Area of Science:

  • Mitochondrial biology
  • Protein homeostasis
  • Structural biology

Background:

  • Mitochondrial heat-shock protein 70 (mtHsp70) and its partners facilitate protein import into the mitochondrial matrix.
  • Tim15 (also known as Zim17/Hep1) is a crucial mtHsp70 partner protein located on the matrix side of the inner mitochondrial membrane.
  • Understanding Tim15's structure and function is key to elucidating mitochondrial protein import mechanisms.

Purpose of the Study:

  • To determine the nuclear magnetic resonance (NMR) structure of the Tim15 core domain.
  • To investigate the role of specific Tim15 residues and structural features in yeast cell growth, mitochondrial protein import, and mtHsp70 aggregation.
  • To correlate Tim15's function in cell growth with its ability to suppress mtHsp70 aggregation.

Main Methods:

  • Nuclear Magnetic Resonance (NMR) spectroscopy to determine the 3D structure of the Tim15 core domain.
  • Site-directed mutagenesis to create Tim15 variants.
  • Functional assays in yeast to assess cell growth, mitochondrial protein import efficiency, and mtHsp70 aggregation suppression.

Main Results:

  • The NMR structure of the Tim15 core domain was determined.
  • A pair of basic residues (Arg 106 and His 107), conserved Asp 111, and a flexible loop (residues 133-137) were identified as important for Tim15 function.
  • These specific regions were found to be critical for yeast cell growth, mitochondrial protein import, and suppression of mtHsp70 aggregation in vivo.

Conclusions:

  • The study elucidated the structure of the Tim15 core domain, revealing key functional regions.
  • Specific residues and structural elements within Tim15 are essential for maintaining yeast cell viability and mitochondrial protein import.
  • Tim15's role in suppressing mtHsp70 aggregation is strongly linked to its function in cell growth, though its primary role remains under investigation.

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