FIG. 1.

Chromosomally encoded ApbE from S. typhimurium LT2 is located in the inner membrane. (A) Immunoblot of whole-cell (WC), soluble cytoplasmic and periplasmic (SOL), total membrane (TM), inner membrane (IM), and outer membrane (OM) fractions. Cellular fractions were prepared as described in Materials and Methods. Western analysis with polyclonal antibodies against ApbE (1:5,000 dilution) was performed (14). (B) Representative membrane separation profile from S. typhimurium LT2. Inner and outer membranes were fractionated by sucrose density equilibration. The protein concentration, NADH oxidase activity, and sucrose concentration values are shown. The fractions pooled and used in Fig. 1A are indicated.