title: The staphylococcal superantigen-like protein 7 binds IgA and complement C5 and inhibits IgA-Fc alpha RI binding and serum killing of bacteria.
abstract: The staphylococcal superantigen-like proteins (SSLs) are close relatives of the superantigens but are coded for by a separate gene cluster within a 19-kb region of the pathogenicity island SaPIn2. rSSL7 (formally known as SET1) bound with high affinity (K(D), 1.1 nM) to the monomeric form of human IgA1 and IgA2 plus serum IgA from primate, pig, rat, and horse. SSL7 also bound the secretory form of IgA found in milk from human, cow, and sheep, and inhibited IgA binding to cell surface FcalphaRI (CD89) and to a soluble form of the FcalphaRI protein. In addition to IgA, SSL7 bound complement factor C5 from human (K(D), 18 nM), primate, sheep, pig, and rabbit serum, and inhibited complement-mediated hemolysis and serum killing of a Gram-negative organism Escherichia coli. SSL7 is a superantigen-like protein secreted from Staphylococcus aureus that blocks IgA-FcR interactions and inhibits complement, leading to increased survival of a sensitive bacterium in blood.
authors.affiliation: Centre for Molecular Biodiscovery and School of Medical Sciences, University of Auckland, Auckland, New Zealand.
authors.forename: Ries
authors.initials: R
authors.lastname: Langley
authors.forename: Bruce
authors.initials: B
authors.lastname: Wines
authors.forename: Natasha
authors.initials: N
authors.lastname: Willoughby
authors.forename: Indira
authors.initials: I
authors.lastname: Basu
authors.forename: Thomas
authors.initials: T
authors.lastname: Proft
authors.forename: John D
authors.initials: JD
authors.lastname: Fraser
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism* / Q000494:pharmacology; D001667:Binding, Competitive / Q000276:immunology; D002417:Cattle; D003126:Colostrum / Q000276:immunology / Q000378:metabolism; D003182:Complement C5 / Q000378:metabolism*; D005098:Exotoxins / Q000378:metabolism / Q000494:pharmacology; D006461:Hemolysis / Q000276:immunology; D006801:Humans; D007070:Immunoglobulin A / Q000097:blood / Q000378:metabolism*; D007071:Immunoglobulin A, Secretory / Q000378:metabolism; D051379:Mice; D008895:Milk, Human / Q000276:immunology / Q000378:metabolism; D008969:Molecular Sequence Data; D002679:Pan troglodytes; D010215:Papio; D011485:Protein Binding / Q000276:immunology; D011817:Rabbits; D051381:Rats; D011961:Receptors, Fc / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D012463:Saliva / Q000276:immunology / Q000378:metabolism; D015610:Serum Bactericidal Test; D012756:Sheep; D013211:Staphylococcus aureus / Q000254:growth & development / Q000276:immunology*; D018089:Superantigens / Q000378:metabolism* / Q000494:pharmacology; D013552:Swine; D013666:Tears / Q000276:immunology / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D001426:Bacterial Proteins; D003182:Complement C5; D005098:Exotoxins; C036832:Fc(alpha) receptor; D007070:Immunoglobulin A; D007071:Immunoglobulin A, Secretory; D011961:Receptors, Fc; D018089:Superantigens; C416085:staphylococcal exotoxin 1