TprCC contains the β-barrel of TprC and forms a trimer. (A to C) CD spectroscopy, heat modifiability, and TX-114 phase partitioning of TprCN and TprCC. Aq and Det, aqueous and detergent-enriched phases, respectively. (D) Quenching of Tb(DPA)33− encapsulated within LUVs following incubation with TprCFl, TprCN, TprCC, and E. coli OmpF. (E) SDS-PAGE of unboiled TprCN and TprCC (asterisk indicates TprCC trimer). Numbers at left in panels B and E are molecular masses in kilodaltons.