Thinking outside the Osp(G)--kinase activation by E2-ubiquitin.

OspG is a secreted effector kinase from the human pathogen Shigella that is required for the reduction of immune responses during Shigella infection. A new study in The EMBO Journal provides a co-crystal structure of OspG bound to UbcH5c similar to Ub, revealing how a bacterial kinase can be activated by the host ubiquitin conjugation machinery. These results provide molecular insight into an enigmatic microbial virulence factor that thwarts the host immune surveillance system to cause disease.