Fig 5.

Urease activity of purified membranes. Wild-type and ΔarsS bacteria were incubated at pH 4.5 or 7.4 for 30 min. Bacteria were lysed, and membranes were isolated and purified. The total urease activity of the membrane fractions was measured by quantifying the release of [¹⁴C]O₂ from [¹⁴C]urea. There was an increase in the level of urease activity in the membrane fraction of the wild-type bacteria after incubation in acid that was abolished in ΔarsS bacteria, in agreement with the Western blot data obtained from identical incubation and membrane isolation experiments (n = 3).