YopM

YopM is a type III secretion system effector protein produced by pathogenic Yersinia species, including Yersinia pestis, Yersinia pseudotuberculosis, and Yersinia enterocolitica. Like other Yop proteins, YopM is synthesized by the bacterium and delivered into host cells through the virulence plasmid–encoded type III secretion system. Within the host, YopM localizes to the cytosol and can accumulate in the nucleus. The protein contains a leucine-rich repeat (LRR) domain, a common feature of many type III effectors involved in protein-protein interactions.

Biochemically, YopM interacts with host serine/threonine kinases, notably the RSK (S6K) and PKN families. By binding these kinases, YopM is thought to act as a molecular scaffold that perturbs signaling pathways related to innate immune responses and cytoskeletal regulation, thereby aiding bacterial evasion of host defenses. The exact downstream effects can vary by host cell type and bacterial strain, and the precise mechanisms remain an area of active research.

Genetically, YopM is encoded on the Yersinia virulence plasmid pCD1 (also called pYV), together with other Yop effectors. In animal models, yopM mutants often display attenuated virulence, supporting a contributory role in disease, though YopM is usually not solely responsible for virulence.

Overall, YopM exemplifies the Yersinia strategy of deploying type III secretion system effectors to modulate host signaling and immune responses. Ongoing studies seek to clarify its exact molecular targets and context-dependent effects across species.