Figure 8.

Schematic representation of β-barrel protein assembly in bacteria, humans, and yeast. In bacteria, Omp85, together with factors facing the periplasm, is necessary and sufficient for assisting correct assembly of β-barrel into the bacterial outer membrane (Voulhoux et al., 2003; Ruiz et al., 2005; Wu et al., 2005). In humans, Metaxin 1 and Metaxin 2 are associated with the mitochondrial outer membrane as part of an uncharacterized ∼600-kDa complex (Kozjak-Pavlovic et al., 2007) and assist Sam50 in assembling β-barrel proteins into the outer membrane. In yeast, Sam35 and Sam37 associate directly with Sam50 to from the SAM_core complex. Sam35 assists Sam50 to bind β-barrel precursors, and Sam37 is important for clearance of β-barrel precursors from the SAM complex, thereby assisting assembly. Sam35 and Sam37 are important for stabilizing each other at the SAM complex, most likely via direct interactions.