Tracheal cytotoxin structural requirements for respiratory epithelial damage in pertussis

Authors

  • Kathryn E. Luker,

    1. Department of Molecular Microbiology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri 63110-1093, USA.
    2. Department of Molecular Biology and Pharmacology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri 63110-1093, USA.
    Search for more papers by this author
  • Andrew N. Tyler,

    1. Department of Chemistry, Harvard University. Cambridge, Massachusetts 02138, USA.
    Search for more papers by this author
  • Garland R. Marshall,

    1. Department of Molecular Biology and Pharmacology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri 63110-1093, USA.
    Search for more papers by this author
  • William E. Goldman

    Corresponding author
    1. Department of Molecular Microbiology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri 63110-1093, USA.
    Search for more papers by this author

Summary

The respiratory epithelial pathology of pertussis (whooping cough) can be reproduced by tracheal cyto-toxin (TCT), a disaccharide-tetrapeptide released by Bordetella pertussis. TCT is a muramyl peptide, a class of peptidoglycan-derived compounds which have many biological activities including adjuvanticity, somnogenicity, pyrogenicity, and cytotoxicity. The structural requirements for muramyl peptides to produce some of these biological effects have been partially characterized. Using in vitro assays with respiratory epithelial cells and tissue, we have previously determined that the disaccharide moiety of TCT is not involved in toxicity and that the side-chain functional groups of diaminopimelic acid (A2pm) are crucial for toxicity. In this study, we determine the importance of every amino acid, functional group and chiral centre in the peptide portion of TCT. Although lactyl tetrapeptides are the most toxic of the TCT fragments, producing dose-response curves identical to TCT, the smallest analogues of TCT which are active in our assay are of the form X-γ-(d)-Glu-meso-A2pm, where X may be an amino acid or a blocking group. Within this active substructure, main-chain chirality and all functional groups are essential for toxicity. This definition of the core region of TCT indicates that the TCT interaction site is unlike almost all other muramyl peptide interaction sites for which structure-activity data are available.

Ancillary