Supporting data for “The role of membrane destabilisation and protein dynamics in BAM catalysed OMP folding”

The folding of β-barrel outer membrane proteins (OMPs) in Gram-negative bacteria is catalysed by the β-barrel assembly machinery (BAM). How lateral opening in the BamA β-barrel, the core component of BAM, catalyses OMP folding remains unclear, with asymmetry in the depth of BamA potentially playing a role by disrupting membrane stability. Here, we use an anti-BamA monoclonal antibody fragment (Fab1) and two disulphide-crosslinked BAM variants (lid-locked (LL), and POTRA-5-locked (P5L)) to dissect these roles. Despite all being lethal in vivo, we show that all catalyse folding in vitro, albeit less efficiently than wild-type BAM. CryoEM revealed that while Fab1 and BAM-P5L trap an open-barrel state, BAM-LL contains a mixture of closed and contorted, partially-open structures. Finally, all three complexes destabilise the lipid bilayer, while BamA alone does not, highlighting the requirement of the BAM lipoproteins for this function. Together the results provide new insights into the role of BAM structure and lipid dynamics in OMP folding