 B. TF-proOmpA intact Native-MS analysis. Mass spectra of TF2 (20 μM; Buffer G), proOmpA (20 μM; pre-treated with 10 mM DTT; Buffer G) or their mixture were acquired in near native conditions using a Synapt G2 mass spectrometer, analyzed using MassLynX 4.1, masses were deconvoluted using MaxEnt 1 and shown together with the theoretical masses and deduced stoichiometries. n=2 biological replicates 