Fig. 3.

The E. coli Δldt3 strain leaks periplasmic enzymes. Western blot analysis of preparations from wild-type, Δlpp and Δldt3 mutant strains grown with maltose (M) or glucose (G) to induce or repress the expression of the MBP, respectively. (a) Precipitated culture supernatants probed with a monoclonal mouse anti-MBP for the presence of the 37 kDa, periplasmic MBP. (b) Whole cells lysates and their corresponding cell culture supernatants probed with a monoclonal rabbit anti-NPT for the expression of the 42 kDa, cytoplasmically located NPT encoded by mutant strains only. The presence of two bands in the MBP blot may be due to proteolysis after release of the protein.