Fig. 7. Heterologous expression of the lpxQ encoded oxidase in S. meliloti and E. coli.

The lpxQ gene was amplified by PCR and ligated into both the shuttle vector pRK404a and into the T7-promoter based vector pET21a+. The resulting constructs, pQN231 and pQN233, were transferred into S. meliloti 1021 and E. coli BL21(DE3)/pLysS, respectively. S. meliloti/pQN231 membranes were prepared from late log phase cells. Membranes of BL21(DE3)/pLysS/pQN233 were obtained from mid log phase cells induced with 1 mM IPTG for 3 h. The membranes (0.5 mg/ml) were assayed for 120 min at 30 °C for their ability to convert 10 μM [¹⁴C]B to [¹⁴C]D-1 under standard oxidase assay conditions.