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Getting into mitochondria.

Ján A Miernyk1

  • 1USDA, Agricultural Research Service, Plant Genetics Research Unit, MO, U.S.A.; Division of Biochemistry, University of Missouri, Columbia, MO 65211, U.S.A.

The Biochemical Journal
|October 30, 2016
PubMed
Summary

Human mitochondrial glutamate dehydrogenase (hGDH) uses a long N-terminal sequence for import into the mitochondrial matrix. Two alpha-helices within this sequence work together to ensure efficient protein localization.

Keywords:
biogenesisbioinformaticsmitochondriasecondary structuretargeting sequence

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Area of Science:

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Background:

  • Human mitochondrial glutamate dehydrogenase (hGDH1 and hGDH2) are nuclear-encoded proteins found in the mitochondrial matrix.
  • These proteins are synthesized in the cytoplasm with a long N-terminal mitochondrial targeting sequence (MTS).

Purpose of the Study:

  • To investigate the role of the N-terminal mitochondrial targeting sequence (MTS) in the import and localization of human mitochondrial glutamate dehydrogenase (hGDH).

Main Methods:

  • Secondary structure prediction analysis of the MTS.
  • Deletion analysis of the MTS to assess protein import and localization.
  • Mutagenesis of MTS cleavage sites.

Main Results:

  • Secondary structure predictions revealed two alpha-helices in the MTS.
  • Individual helices showed limited import/localization ability, but synergistic interaction was observed when both were present.
  • Mutagenesis of cleavage sites blocked presequence removal but not import.

Conclusions:

  • The unusual length and secondary structure of the MTS, particularly the synergistic interaction of its alpha-helices, are crucial for the high matrix levels of hGDH.
  • The MTS effectively directs protein import and localization to the mitochondrial matrix.