title: Calcium-dependent conformation of desmoglein 1 is required for its cleavage by exfoliative toxin.
abstract: In bullous impetigo, Staphylococcus aureus spreads under the stratum corneum of skin by elaboration of exfoliative toxin, which hydrolyzes only one peptide bond in a highly structured calcium-binding domain of desmoglein 1, resulting in loss of its function. We investigated the basis of this exquisite specificity. Exfoliative toxin cannot cleave desmoglein 1 pretreated at 56 degrees C or higher or at low or high pH, suggesting that the proper conformation of desmoglein 1 is critical for its cleavage. Because cleavage occurs in an area of desmoglein 1 stabilized by calcium, we determined if the conformation necessary for cleavage is calcium-dependent. Depletion of calcium from desmoglein 1 completely inhibited its cleavage by exfoliative toxin, even after calcium was added back. A change in conformation of desmoglein 1 by calcium depletion was shown, with immunofluorescence and enzyme-linked immunoassay, by loss of binding of PF sera, which recognize conformational epitopes. This change in conformation was confirmed by tryptophan fluorometry and circular dichroism, and was irreversible with repletion of calcium. These data suggest that the specificity of exfoliative toxin cleavage of desmoglein 1 resides not only in simple amino acid sequences but also in its calcium-dependent conformation.
authors.affiliation: Department of Dermatology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Hanakawa
authors.forename: Trevor
authors.initials: T
authors.lastname: Selwood
authors.forename: Denise
authors.initials: D
authors.lastname: Woo
authors.forename: Chenyan
authors.initials: C
authors.lastname: Lin
authors.forename: Norman M
authors.initials: NM
authors.lastname: Schechter
authors.forename: John R
authors.initials: JR
authors.lastname: Stanley
mesh_terms: D001323:Autoantibodies / Q000494:pharmacology; D015820:Cadherins / Q000737:chemistry* / Q000187:drug effects*; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D002942:Circular Dichroism; D051183:Desmoglein 1; D004797:Enzyme-Linked Immunosorbent Assay; D005083:Exfoliatins / Q000494:pharmacology*; D005470:Fluorometry; D006358:Hot Temperature; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008968:Molecular Conformation; D010392:Pemphigus / Q000276:immunology; D010447:Peptide Hydrolases / Q000494:pharmacology; D011489:Protein Denaturation; D014364:Tryptophan
chemical_list: D001323:Autoantibodies; D015820:Cadherins; D051183:Desmoglein 1; D005083:Exfoliatins; D014364:Tryptophan; D010447:Peptide Hydrolases; D002118:Calcium