Fig. 1: Structural comparison of TamA and BamA β-barrels and outline of OMP assembly assay.
a Structural superimposition of TamA (PDB: 4C0042, residues 266–573, beige) and BamA (PDB: 8BVQ92, residues 424–807, light blue) β-barrels. The calculated RMSDs are listed in Supplementary Table 1. b Outline of the TAM-mediated OMP assembly assay used in this study. The E. coli TAM [His8-TamA (PDB: 4C00] and TamB (based on the structure predicted by AlphaFold2, AF2Complex and MD simulations48,109,110,111) was expressed in vivo, solubilized from a total membrane fraction with n-dodecyl-β-D-maltoside (DDM), and purified on Ni-NTA agarose. The purified TAM was reconstituted into E. coli polar lipid extract (PLE) liposomes, and the predicted topology was validated by trypsin digestion. Based on the results of the trypsin digestion, it is unclear if the N-terminal α-helix of TamB is integrated into a separate liposome (see Source Data file, p. 1). In OMP folding assays, urea denatured OMPs were incubated with the proteoliposomes containing TAM, and their folding and integration into the vesicles was assessed by determining the percent of the protein that was resistant to SDS denaturation in the absence of heat. Part b was created with BioRender.com, released under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International license.
