title: MAG, a novel plasma protein receptor from Streptococcus dysgalactiae.
abstract: The gene encoding a plasma protein receptor from Streptococcus dysgalactiae has been cloned and sequenced. The gene product, with a predicted molecular mass of approx. 44 kDa, binds alpha 2-macroglobulin (alpha 2 M), serum albumin and immunoglobulin G (IgG). By subcloning and expressing various parts of the gene as fusion proteins, we found that the three binding activities reside in discrete domains of the protein. The single IgG-binding domain, localized in the C-terminal part of the molecule, shows high homology to streptococcal type-III Fc receptors. In the middle of the molecule, there is a stretch of 50 amino acids (aa) mediating albumin binding. This region has partial homology with the albumin-binding domains of streptococcal protein G. The alpha 2 M-binding domain is located in the N terminus of the molecule and is composed of a unique aa sequence. We call this trifunctional plasma protein receptor, MAG (binds alpha 2 M, albumin and IgG).
authors.affiliation: Department of Microbiology, Swedish University of Agricultural Sciences, Uppsala.
authors.forename: H
authors.initials: H
authors.lastname: Jonsson
authors.forename: L
authors.initials: L
authors.lastname: Frykberg
authors.forename: L
authors.initials: L
authors.lastname: Rantamäki
authors.forename: B
authors.initials: B
authors.lastname: Guss
mesh_terms: D000418:Albumins / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics*; D001483:Base Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000235:genetics; D005798:Genes, Bacterial / Q000235:genetics*; D008969:Molecular Sequence Data; D010449:Peptide Mapping; D011485:Protein Binding; D011961:Receptors, Fc / Q000737:chemistry* / Q000235:genetics*; D017452:Receptors, IgG / Q000235:genetics; D011993:Recombinant Fusion Proteins; D015183:Restriction Mapping; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013291:Streptococcus / Q000235:genetics*; D000511:alpha-Macroglobulins / Q000378:metabolism
chemical_list: D000418:Albumins; D001426:Bacterial Proteins; D004269:DNA, Bacterial; C087500:MAG protein, Streptococcal; D011961:Receptors, Fc; D017452:Receptors, IgG; D011993:Recombinant Fusion Proteins; D000511:alpha-Macroglobulins