LcrF

LcrF is a transcriptional regulator found in pathogenic Yersinia species, encoded on the virulence plasmid pYV. It belongs to the AraC/XylS family of transcriptional regulators and acts as a master regulator of the virulence gene regulon carried on the same plasmid. LcrF coordinates the expression of genes required for the type III secretion system (T3SS) and its effectors, including lcrV (the V antigen) and the yop family proteins, enabling the bacterium to interact with host cells.

Functionally, LcrF activates transcription of multiple operons that encode components of the T3SS and associated virulence factors. By turning on these genes, LcrF promotes the assembly of the secretion apparatus and the delivery of effector proteins into host cells, which modulates host immune responses and facilitates infection. The regulon controlled by LcrF is tightly linked to environmental conditions that mimic the host, such as elevated temperature and calcium limitation.

Regulation of LcrF itself is integrated into a broader regulatory network. Its activity is influenced by host-like environmental cues, and its expression is coordinated with other plasmid-encoded regulators to ensure virulence genes are expressed at the appropriate stage of infection. Disruption of LcrF function typically attenuates virulence, underscoring its central role in pathogenesis.

In research, LcrF serves as a model for AraC-family virulence regulators and as a potential target for anti-virulence strategies aimed at disarming pathogenic Yersinia without relying on traditional bactericidal approaches. Its study contributes to understanding how bacterial pathogens synchronize gene expression with host-related signals to establish infection.