TcpT localizes to the IM in a TcpR-dependent manner. (A) Periplasmic (P), cytoplasmic (C), IM, and OM fractions from WT V. cholerae probed with fractionation control anti-EpsL (IM marker), anti-TcpC (OM marker), and anti-TcpT antibodies. The specific activity of G6PDH, a cytoplasmic marker, is indicated below each fraction. (B) Periplasmic (P), cytoplasmic (C), IM, and OM fractions from WT and IM TCP biogenesis mutants probed with anti-TcpT antibody. (C) Cytoplasmic (C) and IM fractions of a tcpR deletion mutant complemented with pTcpR-6xHis grown under inducing and noninducing conditions and probed with anti-TcpT antibody.