T3SSYop

T3SSYop is a term used to describe the set of Yersinia outer proteins (Yops) that are secreted by the bacterium’s Type III secretion system (T3SS). The Yop family comprises effector proteins injected into host cells to manipulate signaling, cytoskeletal organization, vesicle trafficking, and innate immune responses, thereby promoting bacterial survival and dissemination. Yersinia species such as Y. pestis, Y. enterocolitica, and Y. pseudotuberculosis encode a T3SS on the pYV plasmid, and expression of yop genes is regulated by environmental cues, including temperature near host body conditions and calcium availability.

The T3SS is a syringe-like complex with a basal body in the bacterial envelope, a needle, and a translocon that inserts into the host cell membrane to deliver unfolded Yops. Chaperones in the bacterial cytoplasm maintain effectors in a secretion-competent state and guide them to the secretion apparatus. Upon contact with a host cell, the translocation pore forms and Yops are translocated into the cytosol, where they disrupt cytoskeletal dynamics, signal transduction, and immune pathways. Certain Yops, such as YopH and YopE, target actin- and focal-adhesion processes to impede phagocytosis; others modulate MAPK or NF-κB signaling or alter vesicular trafficking.

In research, Yops are used to study host-pathogen interactions and the virulence strategies of Gram-negative bacteria. Understanding the T3SSYop repertoire and regulation helps explain the pathogenic differences among Yersinia species and informs strategies for therapeutic intervention.