Primary Citation of Related Structures: 5WHT, 5WHU, 5WHV
PubMed Abstract:
The evolution of virulence traits is central for the emergence or re-emergence of microbial pathogens and for their adaptation to a specific host 1-5 . Typhoid toxin is an essential virulence factor of the human-adapted bacterial pathogen Salmonella Typhi 6,7 , the cause of typhoid fever in humans 8-12 ...
The evolution of virulence traits is central for the emergence or re-emergence of microbial pathogens and for their adaptation to a specific host 1-5 . Typhoid toxin is an essential virulence factor of the human-adapted bacterial pathogen Salmonella Typhi 6,7 , the cause of typhoid fever in humans 8-12 . Typhoid toxin has a unique A 2 B 5 architecture with two covalently linked enzymatic 'A' subunits, PltA and CdtB, associated with a homopentameric 'B' subunit made up of PltB, which has binding specificity for the N-acetylneuraminic acid (Neu5Ac) sialoglycans 6,13 prominently present in humans 14 . Here, we examine the functional and structural relationship between typhoid toxin and ArtAB, an evolutionarily related AB 5 toxin encoded by the broad-host Salmonella Typhimurium 15 . We find that ArtA and ArtB, homologues of PltA and PltB, can form a functional complex with the typhoid toxin CdtB subunit after substitution of a single amino acid in ArtA, while ArtB can form a functional complex with wild-type PltA and CdtB. We also found that, after addition of a single-terminal Cys residue, a CdtB homologue from cytolethal distending toxin can form a functional complex with ArtA and ArtB. In line with the broad host specificity of S. Typhimurium, we found that ArtB binds human glycans, terminated in N-acetylneuraminic acid, as well as glycans terminated in N-glycolylneuraminic acid (Neu5Gc), which are expressed in most other mammals 14 . The atomic structure of ArtB bound to its receptor shows the presence of an additional glycan-binding site, which broadens its binding specificity. Despite equivalent toxicity in vitro, we found that the ArtB/PltA/CdtB chimaeric toxin exhibits reduced lethality in an animal model, indicating that the host specialization of typhoid toxin has optimized its targeting mechanisms to the human host. This is a remarkable example of a toxin evolving to broaden its enzymatic activities and adapt to a specific host.
Organizational Affiliation:
Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT, 06536, USA. jorge.galan@yale.edu.
AA [auth B], CB [auth H], DB [auth H], EB [auth H], KA [auth E],
AA [auth B], CB [auth H], DB [auth H], EB [auth H], KA [auth E], NA [auth F], OA [auth F], PA [auth F], PB [auth J], U [auth A], VA [auth G], WA [auth G]
BA [auth B], CA [auth B], DA [auth B], FA [auth C], FB [auth H],
BA [auth B], CA [auth B], DA [auth B], FA [auth C], FB [auth H], GB [auth H], HA [auth D], JB [auth I], KB [auth I], LA [auth E], LB [auth I], MB [auth I], QA [auth F], QB [auth J], RA [auth F], RB [auth J], SA [auth F], V [auth A], W [auth A], X [auth A], XA [auth G], Y [auth A], YA [auth G]
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