title: Antigenic diversity within a family of M proteins from group A streptococci: evidence for the role of frameshift and compensatory mutations.
abstract: The genes (emm) encoding M proteins, from isolates of group-A streptococci (GAS) serotyped as M52, M53, M80 and M nontypeable (MNT; serologically related to M53 and M80), were examined. Characterization of emm from these GAS revealed some discrepancies with serotyping, illustrating the difficulty in serotype determination when cross-reactions occur. DNA sequences corresponding to the N-terminal region of M proteins from the isolates showed considerable similarity both in the hypervariable region and the repeat regions. We propose that these serotypes form a family of closely related M types. Frameshift mutations in the hypervariable region followed by a corrective (compensatory) frameshift were observed. This may be an effective mechanism for generating antigenic diversity in the M protein.
authors.affiliation: Menzies School of Health Research, Causarina, N.T., Australia.
authors.forename: W A
authors.initials: WA
authors.lastname: Relf
authors.forename: D R
authors.initials: DR
authors.lastname: Martin
authors.forename: K S
authors.initials: KS
authors.lastname: Sriprakash
mesh_terms: D000595:Amino Acid Sequence; D000942:Antigens, Bacterial / Q000235:genetics / Q000276:immunology*; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology*; D001483:Base Sequence; D002352:Carrier Proteins; D004269:DNA, Bacterial; D000939:Epitopes / Q000235:genetics*; D016368:Frameshift Mutation; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013297:Streptococcus pyogenes / Q000235:genetics* / Q000276:immunology
chemical_list: D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D004269:DNA, Bacterial; D000939:Epitopes; C014689:streptococcal M protein