Assembly of β-barrel proteins in the mitochondrial outer membrane

Biochim Biophys Acta. 2015 Jan;1853(1):74-88. doi: 10.1016/j.bbamcr.2014.10.006. Epub 2014 Oct 8.

Abstract

Mitochondria evolved through endosymbiosis of a Gram-negative progenitor with a host cell to generate eukaryotes. Therefore, the outer membrane of mitochondria and Gram-negative bacteria contain pore proteins with β-barrel topology. After synthesis in the cytosol, β-barrel precursor proteins are first transported into the mitochondrial intermembrane space. Folding and membrane integration of β-barrel proteins depend on the mitochondrial sorting and assembly machinery (SAM) located in the outer membrane, which is related to the β-barrel assembly machinery (BAM) in bacteria. The SAM complex recognizes β-barrel proteins by a β-signal in the C-terminal β-strand that is required to initiate β-barrel protein insertion into the outer membrane. In addition, the SAM complex is crucial to form membrane contacts with the inner mitochondrial membrane by interacting with the mitochondrial contact site and cristae organizing system (MICOS) and shares a subunit with the endoplasmic reticulum-mitochondria encounter structure (ERMES) that links the outer mitochondrial membrane to the endoplasmic reticulum (ER).

Keywords: Bacteria; Beta-barrel; Mitochondria; Outer membrane; Protein assembly; Protein import.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Endoplasmic Reticulum / chemistry
  • Mitochondrial Membrane Transport Proteins / chemistry*
  • Mitochondrial Membranes / chemistry*
  • Porins / chemistry
  • Protein Structure, Secondary
  • Protein Transport
  • Saccharomyces cerevisiae Proteins / chemistry

Substances

  • Mitochondrial Membrane Transport Proteins
  • Porins
  • Saccharomyces cerevisiae Proteins
  • Tom40 protein, S cerevisiae