N255 is a key residue for recognition by a monoclonal antibody which protects against Yersinia pestis infection

Mab7.3 to Yersinia pestis LcrV antigen (LcrVYpe) protected J774A.1 macrophages in vitro from killing by a Yersinia pseudotuberculosis strain expressing LcrVYpe. Of 4 site-directed mutations in the coiled-coil region (148–169) and 7 mutations in the 225–255 sequence of LcrVYpe, only the mutation of N255 to D255, abrogated the binding of Mab7.3 and reduced its protective capacity against plague. Since the Mab7.3 epitope in LcrVYpe (135–275) encompasses a region (136–180) thought to be exposed on the injectisome, we suggest that Mab7.3 protects by binding to LcrVYpe and interfering with protein–protein interactions necessary for type three secretion.