Part of the binding-protein-dependent transport system for D-methionine and the toxic methionine analog alpha-methyl-methionine. Probably responsible for the translocation of the substrate across the membrane. (Microbial infection) Probably transports the toxic C-terminal region of CdiA from E.coli strain MHI813 across the inner membrane to the cytoplasm, where CdiA has a toxic effect. Toxin transport is strain-specific, mutations in this gene do not confer resistance to several other tested CdiA toxins. Disruption confers resistance to cellular contact-dependent growth inhibition (CDI) CdiA of E.coli strain MHI813, but not to several other tested CdiA toxins. Belongs to the binding-protein-dependent transport system permease family. CysTW subfamily. Truncated N-terminus.