Modular Assembly of Mitochondrial β-Barrel Proteins.

Mitochondrial β-barrel proteins fulfill crucial roles in the biogenesis and function of the cell organelle. They mediate the import and membrane insertion of proteins and transport of small metabolites and ions. All β-barrel proteins are made as precursors on cytosolic ribosomes and are imported into mitochondria. The β-barrel proteins fold and assemble with partner proteins in the outer membrane. The in vitro import of radiolabelled proteins into isolated mitochondria is a powerful tool to investigate the import of β-barrel proteins, the folding of the β-barrel proteins, and their assembly into protein complexes. Altogether, the in vitro import assay is a versatile and crucial assay to analyze the mechanisms of the biogenesis of mitochondrial β-barrel proteins.