The Yop virulon allows Yersinia spp. to resist the immune response of the host by injecting harmful proteins into host cells. It is composed of four elements: (i) type III secretion machinery called Ysc; (ii) a set of proteins required to translocate the effector proteins inside the eukaryotic cells; (iii) a control system, and (iv) six Yop effector proteins.
Bleves, S., & Cornelis, G. (2000). How to survive in the host: the Yersinia lesson. Microbes and Infection : a journal on infectious agents and host defenses, 2(12), 1451-1460. https://doi.org/10.1016/S1286-4579(00)01300-9 (Original work published 2000)