Release of ATP from M. hominis infected HeLa cells. HeLa cells were incubated with M. hominis (Mhom), membrane proteins (mem+), membrane proteins without OppA (mem-), purified OppA and OppAΔP-loop-mutant for 1.5 to 48 h as described in the Material and Methods section. Infection assays were done in the presence (A) or absence (B) of 500 μM ATPase inhibitor 4',4', diisothiocyanostilbene 2'2'disulfonic acid (DIDS). The ATP concentration in the culture supernatants was measured using a luciferase assay (ATP Determination Kit). Results are expressed as means ± SD of triplicates.