title: Functional mapping of community-acquired respiratory distress syndrome (CARDS) toxin of Mycoplasma pneumoniae defines regions with ADP-ribosyltransferase, vacuolating and receptor-binding activities.
abstract: Community-acquired respiratory distress syndrome (CARDS) toxin from Mycoplasma pneumoniae is a 591-amino-acid virulence factor with ADP-ribosyltransferase (ADPRT) and vacuolating activities. It is expressed at low levels during in vitro growth and at high levels during colonization of the lung. Exposure of experimental animals to purified recombinant CARDS toxin alone is sufficient to recapitulate the cytopathology and inflammatory responses associated with M. pneumoniae infection in humans and animals. Here, by molecular modelling, serial truncations and site-directed mutagenesis, we show that the N-terminal region is essential for ADP-ribosylating activity. Also, by systematic truncation and limited proteolysis experiments we identified a portion of the C-terminal region that mediates toxin binding to mammalian cell surfaces and subsequent internalization. In addition, the C-terminal region alone induces vacuolization in a manner similar to full-length toxin. Together, these data suggest that CARDS toxin has a unique architecture with functionally separable N-terminal and C-terminal domains.
authors.affiliation: Department of Microbiology and Immunology/Center for Airway Inflammation Research, The University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA.
authors.forename: Thirumalai R
authors.initials: TR
authors.lastname: Kannan
authors.forename: Manickam
authors.initials: M
authors.lastname: Krishnan
authors.forename: Kumaraguruparan
authors.initials: K
authors.lastname: Ramasamy
authors.forename: Argentina
authors.initials: A
authors.lastname: Becker
authors.forename: Olga N
authors.initials: ON
authors.lastname: Pakhomova
authors.forename: P John
authors.initials: PJ
authors.lastname: Hart
authors.forename: Joel B
authors.initials: JB
authors.lastname: Baseman
mesh_terms: D036002:ADP Ribose Transferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020816:Amino Acid Motifs; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001427:Bacterial Toxins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008958:Models, Molecular; D009177:Mycoplasma pneumoniae; D009243:NAD / Q000378:metabolism; D017434:Protein Structure, Tertiary; D059748:Proteolysis; D037521:Virulence Factors / Q000737:chemistry / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; C546120:CARDS toxin, Mycoplasma pneumoniae; D037521:Virulence Factors; D009243:NAD; D036002:ADP Ribose Transferases