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Spatial orientation of mitochondrial processing peptidase and a preprotein revealed by fluorescence resonance energy

Tomonori G Nishino1, Ken Kitano, Katsuhiko Kojima

  • 1Department of Chemistry, Faculty of Science, Kyushu University, Fukuoka 812-8581, Japan.

Journal of Biochemistry
|April 12, 2007
PubMed

Insights

Mitochondrial processing peptidase (MPP) orients preproteins using a specific cleft. This interaction involves the glycine-rich loop of alpha-MPP, guiding the polypeptide chain.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Protein Structure

Background:

  • Mitochondrial processing peptidase (MPP) is crucial for protein import into mitochondria.
  • MPP removes N-terminal signal prepeptides from mitochondrial preproteins.
  • Previous crystal structures lacked spatial orientation details of preproteins within MPP.

Purpose of the Study:

  • To determine the spatial orientation of preproteins relative to MPP.
  • To elucidate the interaction mechanism between preproteins and MPP subunits.

Main Methods:

  • Fluorescence Resonance Energy Transfer (FRET) analysis was employed.
  • EGFP-fused yeast aconitase presequence (preEGFP) was used as a preprotein model.
  • Regiospecific CPM-labeled yeast MPP (alpha-MPP and beta-MPP) was utilized.

Main Results:

  • FRET efficiencies indicated distances of 48 Å and 50 Å between EGFP and labeled residues on beta-MPP.
  • In silico modeling based on FRET data and crystal structure was performed.
  • The model revealed preprotein C-terminal orientation away from the MPP cavity, interacting with the alpha-MPP glycine-rich loop.

Conclusions:

  • MPP orients preproteins at a specific cleft between its catalytic domain and the glycine-rich loop.
  • This interaction facilitates the "pinching" of the extended polypeptide chain.
  • The findings provide insights into the mechanism of mitochondrial protein processing.

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