Although not significantly enriched within the set of directly PhoPQ-regulated genes , the functional class related to pathogenicity and virulence also contained potential PhoPQ-dependent targets ( pagC , mgtC , virK , and STM0306 ) .
STM0306 , a fourth PhoPQ-regulated gene that is involved in pathogenicity , is a paralog of the S. typhimurium SapA protein , which was shown to play a role in virulence ( Parra-Lopez et al. 1993 ) .