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Functional analysis of human metaxin in mitochondrial protein import in cultured cells and its relationship with the

K M Abdul1, K Terada, M Yano

  • 1Department of Molecular Genetics, Kumamoto University School of Medicine, Honjo 2-2-1, Kumamoto, 860-0811, Japan.

Biochemical and Biophysical Research Communications
|October 12, 2000
PubMed

Insights

Metaxin, an outer mitochondrial protein, impairs preprotein import when overexpressed. This study confirms metaxin

Area of Science:

  • Mitochondrial biology
  • Protein import mechanisms
  • Cellular and molecular biology

Background:

  • Metaxin is an outer mitochondrial membrane protein implicated in organelle protein import.
  • The distribution of metaxin mRNA in human tissues differs from that of the translocase component Tom20.
  • Previous studies indicated that overexpression of Tom20 inhibits mitochondrial preprotein import.

Purpose of the Study:

  • To investigate the role of human metaxin in mitochondrial protein import.
  • To determine the effect of metaxin overexpression on preprotein import and processing in COS-7 cells.
  • To examine the potential association of metaxin with the TOM complex.

Main Methods:

  • Overexpression of human metaxin and its cytosolic domain in COS-7 cells.
  • Analysis of mitochondrial preprotein import and processing.
  • Blue native polyacrylamide gel electrophoresis (PAGE) to analyze protein complex formation.

Main Results:

  • Overexpression of metaxin led to impaired mitochondrial import and accumulation of preproteins.
  • Coexpression of metaxin with Tom20 did not result in further inhibition of preprotein import.
  • Blue native PAGE showed metaxin migrating independently of the TOM complex (Tom40, Tom22, Tom20).

Conclusions:

  • Metaxin plays a role in preprotein import into mammalian mitochondria.
  • Metaxin does not appear to associate with the TOM complex.
  • The cytosolic domain of metaxin also contributes to the inhibition of preprotein import.

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