Fig. 1.

BamA lowers the kinetic barrier to OMP folding imposed by PE head groups. Unfolded OMPs were folded into LUVs containing 100% PC or 95% PC + 5% PE or 80% PC + 20% PE in the absence or presence of one of the following prefolded OMPs as indicated: BamA, BamAΔP1-4, OmpA or OmpX. The client OMP is indicated in each panel, and its total concentration was 4 or 2 μM without or with prefolded OMP, respectively, at a constant lipid:protein mole ratio of 800:1. Samples were taken at indicated times and quenched with SDS/PAGE loading buffer. SDS/PAGE gels (SI Appendix, Fig. S2) were analyzed by densitometry and fraction folded was plotted as the ratio of the folded band intensity divided by the boiled band intensity. Lines indicate fitted curves; black, no prefolded OMP; green, prefolded BamA or BamAΔP1-4; orange, prefolded OmpX; magenta, prefolded OmpA. Each experiment was conducted in triplicate, and one representative data set is shown for each condition. SI Appendix, Fig. S3 shows representative data that includes the extended time points collected for the slower kinetic data, demonstrating that folding was collected to saturation. The average fit values with SDs are reported in SI Appendix, Tables S1–S4 and Fig. S4.