Preparation of liposomes

The respective lipids were mixed in chloroform and dried under a nitrogen gas flow (1 mg/ml for liposome permeabilization assays, 5 mg/ml for CD measurements). The lipids were resuspended in 1 ml of the respective buffer, sonicated in a sonication bath for 2 min, and subjected to ten freeze and thaw cycles before the suspension was subjected to eleven rounds of extrusion using a 100‐nm filter membrane unless indicated otherwise.

The following two lipid compositions were used in our studies, all presented as mass percentage. OMM lipids were prepared by mixing 46% l‐α‐phosphatidylcholine (PC), 25% l‐α‐phosphatidylethanolamine (PE), 11% l‐α‐phosphatidylinositol (PI), 10% 1,2‐dioleyl‐sn‐glycero‐3‐phospho‐L‐serine, and 7% 1,1’,2,2’‐tetra‐(9Z‐octadecenoyl)cardiolipin. According to the manufacturer, E. coli polar lipid extract consists of 67% phosphatidylethanolamine (PE), 23.2% phosphatidylglycerol (PG), and 9.8% cardiolipin (CL). 2–10% 18:1 DGS‐NTA (Ni²⁺) was added to the lipid mixtures as indicated in the corresponding method sections. All lipids were obtained from Avanti Polar Lipids.