Figure 3.

LptA momomeric mutant (LptA_m) is functional in vivo. The araBp-lptAB arabinose dependent conditional mutant in which the chromosomal lptAB genes are under the control of the arabinose dependent araBp promoter, is complemented by the lptA _m -lptB allele. The steady-state levels of LptA and LptAm are analyzed by Western blotting. (a) araBp-lptAB cells expressing wild type and mutant lptA _m alleles were grown in LD with 0.2% arabinose and 100 μg/ml ampicillin. Serial dilutions in microtiter plates were replica plated on the same medium with (+ara) or without (−ara) arabinose. Serial dilutions are indicated on the top of the panel. (−): empty vector. (b) araBp-lptAB cells expressing wild type and mutant lptA _m alleles grown in LD with 0.2% arabinose and 100 μg/ml ampicillin up to an optical density at 600 nm (OD₆₀₀) of 0.2, were diluted 350-fold in fresh medium (supplemented with ampicillin), with (ara) or without (no ara) 0.2% arabinose. Growth was monitored by measuring OD₆₀₀. (c) araBp-lptAB cells bearing plasmids expressing lptAB, lptA _m -B and empty vector (−) were grown with (+ara) or without (−ara) arabinose as described in panel B and samples were collected at 300 min. The AM604 (wild type) strain was grown in LD up to OD₆₀₀ of 0.6. Samples were analyzed by Western blotting using anti-LptA antibodies. Equal amount of cells (0.24 OD₆₀₀ units) were loaded onto each lane.