Nucleotide substitutions and small-scale insertion produce size and antigenic variation in group A streptococcal M1 protein

Mol Microbiol. 1993 May;8(5):981-91. doi: 10.1111/j.1365-2958.1993.tb01642.x.


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.

Publication types

  • Comparative Study

MeSH terms

  • Amino Acid Sequence
  • Antibodies, Bacterial / immunology
  • Antigen-Antibody Reactions
  • Antigenic Variation / genetics*
  • Antigens, Bacterial / genetics*
  • Bacterial Outer Membrane Proteins*
  • Bacterial Proteins / genetics*
  • Base Sequence
  • Carrier Proteins*
  • Genes, Bacterial*
  • Molecular Sequence Data
  • Open Reading Frames
  • Point Mutation
  • Sequence Alignment
  • Sequence Homology
  • Streptococcus pyogenes / genetics*


  • Antibodies, Bacterial
  • Antigens, Bacterial
  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • Carrier Proteins
  • streptococcal M protein

Associated data

  • GENBANK/Z21845