Membrane Defects Accelerate Outer Membrane β-Barrel Protein Folding

[Image: see text] Outer membrane β-barrel proteins spontaneously fold into lipid bilayers with rates of folding that are strongly influenced by the physical properties of the membrane. We show that folding is accelerated when the bilayer is at the phase transition temperature, because of the coexistence of lipid phase domains and the high degree of defects present at domain boundaries. These results are consistent with previous observations of faster folding into thin and highly curved membranes, which also contain a higher prevalence of defects. The importance of defects in β-barrel folding provides insight into the intrinsic folding process and the biological assembly pathway.