The structure of the TOM core complex in the mitochondrial outer membrane

Area of Science:

• Mitochondrial Biology
• Structural Biology
• Biochemistry

Background:

• Significant advances in understanding translocase of the outer mitochondrial membrane (TOM)-mediated protein translocation into mitochondria.
• Biochemical and biophysical studies of TOM have been interpreted based on recent structural data.

Purpose of the Study:

• To compare the subnanometer structure of the Neurospora crassa TOM core complex with that of Saccharomyces cerevisiae.
• To provide a structural basis for interpreting existing biochemical and biophysical data on mitochondrial protein import.

Main Methods:

• Cryoelectron microscopy to determine high-resolution structures of TOM core complexes.
• Comparative structural analysis of TOM complexes from N. crassa and S. cerevisiae.

Main Results:

• Both N. crassa and yeast TOM core complexes form remarkably well-conserved symmetrical dimers.
• Each dimer consists of 10 membrane protein subunits.
• Structural data validate predictions of weakly stable regions in the Tom40 subunit's transmembrane β-barrel, indicating β-strands at protein-protein interaction interfaces.

Conclusions:

• The high degree of structural conservation suggests a common mechanism for TOM function across different species.
• Structural insights into the TOM complex, particularly Tom40, advance our understanding of mitochondrial protein import pathways.