A. Analysis of proOmpA:SecB and TF:proOmpA:SecB complexes by native-MS. SecB4 (30 μM; Buffer G), SecB4 (40 μM) and proOmpA (20 μM; pre-treated with 10 mM DTT; buffer G) and of SecB4 (40 μM), proOmpA (20 μM) and TF2 (20 μM) in buffer G were analyzed as in Fig. 2B (raw data in Fig. EV3). n=2 biological replicates. 