FIG. 5.

Lysis of E. coli by overexpression of wild-type or carboxy-terminal truncated PBP 5. Overnight cultures of E. coli CS109 containing either pPJ5 (to express wild-type PBP 5) or pPJ5D (to express PBP 5 lacking the carboxy-terminal membrane anchor) were diluted 1:500 into fresh LB broth and incubated with shaking in flasks at 37°C to an A₆₀₀ of 0.2. At that point, arabinose was added at different final concentrations to induce different levels of PBP expression. Samples for PBP quantification were collected before and 30 mins after induction of protein expression, and the amounts of wild-type and truncated PBP 5 expressed from equal numbers of cells were quantified by comparing the intensities of PBP bands after separation by SDS-PAGE. The amount of wild-type PBP 5 expressed from a single chromosomal copy of the dacA gene was regarded to be the 1× expression level, and amounts of overexpression of the wild-type and truncated PBP 5 forms are expressed as multiples of this baseline figure. PBP 5 (1× expression), ⧫; PBP 5 (12× expression), ■; PBP 5 (65× expression), ▾; carboxy-truncated PBP 5 (4× expression), ○; carboxy-truncated PBP 5 (7× expression), ▵.