Fig. 7.
Model of RicI-mediated conjugation inhibition in Salmonella. (Left) Under regular growth conditions (no membrane stress), the Rcs system is inactive and RprA is not produced. Therefore, RprA cannot activate rpoS and ricI will not be expressed. Expression and assembly of the pSLT conjugation apparatus is permitted. (Right) When the Rcs system is activated (e.g., by bile salts or A22), full-length RprA will activate the rpoS mRNA leading to σS production. σS activates the transcription of ricI, and the ricI mRNA can be activated by the processed RprA variant. Finally, RicI interacts with TraV to inhibit assembly of the pSLT conjugation pilus.