The suppressive effects of spermine NONOate on PhoP-dependent gene transcription appear to be directly related to the production of RNS because the polyamine base spermine did not suppress the acid-induced expression of the PhoP-activated loci lpxO , pqaA , and pcgE ( fig. 6B -- D ) .
The acid-inducible expression of the PhoP-activated loci lpxO , pqaA and pcgE were monitored in the presence or absence of 250 mM spermine , 250 mM spermine NONOate or 500 mM NaNO2 ( B -- D ) .