Fig. 4: Additive effect of BAM inhibition by disulfide-locking and binding of Fab1.

a 7.1 Å cryoEM map of the Fab1-bound LL-BAM in a lateral-open (contorted) conformation at a contour of 9.5σ, coloured by subunit. The lateral gate is open and POTRA-5 occludes the BamA barrel (schematic inset). b Cartoon representation of the corresponding atomic model at the lateral gate, superimposed on the segmented density for the β-barrel and POTRA-5 of BamA. To satisfy the disulphide in this conformation, eL1 must bend back into the barrel to contact eL6. c The same density viewed from the periplasmic side, showing that the BamA lumen is blocked by POTRA-5 in this conformation. Structural panels made using UCSF ChimeraX⁷⁶. Segmenting and colouring performed with corresponding atomic models. Less well-resolved regions and the micelle have been masked. d and e Quantification of SDS–PAGE band-shift assays shown in Supplementary Fig. 15 for d tOmpA and e OmpX folding catalysed by BAM-P5L + Fab1 (green, solid circles) and BAM-LL + Fab1 (blue, solid circles). Data for WT BAM (black, open circles), BAM-P5L (green, open circles) and BAM-LL (blue, open circles), from Fig. 1, are shown for comparison. Data markers represent the average folded fractions calculated from at least two repeats (The number of replicates is shown in Supplementary Table 1) and dashed lines are single exponential fits of the data. Error bars represent range of values covered by the replicates. f and g The initial rates, calculated by applying a linear fit to the first 5% of fitted folding data, were normalised to the mean value for WT BAM, and are shown for f tOmpA and g OmpX folding. Bars represent the mean value for each condition, with values for each replicate shown as grey points. Average initial rates, normalised data and ranges are listed Supplementary Table 1. Folding yields after 24 h are reported in Supplementary Table 2. Figures labelled with “BAM” refer to the full BAM complex (BamABCDE), whilst “BamA” is just BamA alone. Source data for d–g are provided as a source data file.