Gene

Biogenesis

Cell biology

Membrane protein

Biology

Barrel (horology)

Materials science

Biochemistry

Mitochondrial membrane transport protein

Transport protein

Bacterial outer membrane

Membrane

Translocase of the inner membrane

Escherichia coli

Composite material

Translocase of the outer membrane

Chemistry

Biophysics

Science

The biogenesis of mitochondria, chloroplasts, and Gram-negative bacteria requires the insertion of β-barrel proteins into the outer membranes. Homologous Omp85 proteins are essential for membrane insertion of β-barrel precursors. It is unknown if precursors are threaded through the Omp85-channel interior and exit laterally or if they are translocated into the membrane at the Omp85-lipid interface. We have mapped the interaction of a precursor in transit with the mitochondrial Omp85-channel Sam50 in the native membrane environment. The precursor is translocated into the channel interior, interacts with an internal loop, and inserts into the lateral gate by β-signal exchange. Transport through the Omp85-channel interior followed by release through the lateral gate into the lipid phase may represent a basic mechanism for membrane insertion of β-barrel proteins.

Membrane protein insertion through a mitochondrial β-barrel gate