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Updated: May 17, 2026

From Constructs to Crystals – Towards Structure Determination of β-barrel Outer Membrane Proteins
Published on: July 4, 2016
Characterization of the insertase for β-barrel proteins of the outer mitochondrial membrane
Astrid Klein1, Lars Israel, Sebastian W K Lackey
1Max-Planck Institut für Biochemie, Abteilung für zelluläre Biochemie, D-82152 Martinsried, Germany.
Abstract:
The TOB-SAM complex is an essential component of the mitochondrial outer membrane that mediates the insertion of β-barrel precursor proteins into the membrane. We report here its isolation and determine its size, composition, and structural organization. The complex from Neurospora crassa was composed of Tob55-Sam50, Tob38-Sam35, and Tob37-Sam37 in a stoichiometry of 1:1:1 and had a molecular mass of 140 kD. A very minor fraction of the purified complex was associated with one Mdm10 protein. Using molecular homology modeling for Tob55 and cryoelectron microscopy reconstructions of the TOB complex, we present a model of the TOB-SAM complex that integrates biochemical and structural data. We discuss our results and the structural model in the context of a possible mechanism of the TOB insertase.
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