title: Nucleotide substitutions and small-scale insertion produce size and antigenic variation in group A streptococcal M1 protein.
abstract: The presence of M protein on the surface of group A streptococci (GAS) confers the ability of the cell to resist phagocytosis in the absence of type-specific antibodies. It undergoes antigenic variation with more than 80 different serotypes having been defined. We have sequenced the M protein gene (emm1.1) from strain CS190 and present evidence that individual nucleotide substitutions are responsible for sequence variation in the N-terminal non-repeat region of emm1.1 and these substitutions have altered antibody recognition of opsonic epitopes. The N-terminal non-repeat domains of two other closely related strains, 71-155 and 76-088, were found to have sequence identical to emm1.1 with the addition of a 21 bp insert. This study provides the first evidence that nucleotide substitutions and small insertions are responsible for size and antigenic variation in the N-terminal non-repeat domain of the M protein of GAS.
authors.affiliation: Department of Food Science and Nutrition, University of Minnesota, St. Paul 55108.
authors.forename: M P
authors.initials: MP
authors.lastname: Harbaugh
authors.forename: A
authors.initials: A
authors.lastname: Podbielski
authors.forename: S
authors.initials: S
authors.lastname: Hügl
authors.forename: P P
authors.initials: PP
authors.lastname: Cleary
mesh_terms: D000595:Amino Acid Sequence; D000907:Antibodies, Bacterial / Q000276:immunology; D000937:Antigen-Antibody Reactions; D000940:Antigenic Variation / Q000235:genetics*; D000942:Antigens, Bacterial / Q000235:genetics*; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002352:Carrier Proteins; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D017354:Point Mutation; D016415:Sequence Alignment; D017385:Sequence Homology; D013297:Streptococcus pyogenes / Q000235:genetics*
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; C014689:streptococcal M protein