PROS1 and pneumonic plague: In another example, RovA is a member of the MarR/SlyA family, which regulates expression of inv (an adhesion and invasion factor) in the enteric pathogens Yersinia enterocolitica and Yersinia pseudotuberculosis, as well as expression of the psa locus of Yersinia pestis, the causative agent of bubonic and pneumonic plague.