Reconstitution of the E. coli Membrane Beta-Barrel Assembly Machine from Purified Components

β-barrel membrane proteins perform important functions in the outer membranes of Gram-negative bacteria and in the mitochondria and chloroplasts of eukaryotes. Cellular machines that have been conserved from bacteria to humans assemble these proteins by an unknown mechanism. The components of the β-barrel assembly machine (Bam) in E. coli have been identified, but it has been difficult to study their function in vivo because they catalyze an essential process; mutations in proteins involved in the assembly pathway are often lethal or produce pleiotropic phenotypes that do not reveal the specific roles of the individual proteins. This study describes an in vitro reconstitution of the activity of the Bam complex and the use of this assay to determine how the Bam proteins contribute to the assembly of the complex itself.