A secreted streptococcal cysteine protease can cleave a surface-expressed M1 protein and alter the immunoglobulin binding properties

Res Microbiol. 1998 Sep;149(8):539-48. doi: 10.1016/s0923-2508(99)80001-1.


Previous studies of recent clinical isolates of serotype M1 group A streptococci indicated that they display two patterns of non-immune human IgG subclass binding reactivity associated with their M1 protein. One group reacted with all four IgG subclasses (type IIo), while the second group expressed an M1 protein reacting preferentially with human IgG3 (type IIb). In this study, we have demonstrated that a cysteine protease, SpeB, present in culture supernatants of M1 serotype group A streptococcal isolates expressing type IIb IgG binding protein, can convert a recombinant Emm1 protein from a type IIo functional profile to a type IIb profile by removal of 24 amino acids from the N-terminus of the mature M1 protein. Furthermore, SpeB can convert bacteria expressing IgG binding proteins of the type IIo phenotype into those expressing type IIb proteins. The role of the cysteine protease as the central bacterial enzyme in this posttranslational modification event was confirmed by generation of an isogenic SpeB-negative mutant.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Antigens, Bacterial / immunology
  • Antigens, Bacterial / metabolism*
  • Bacterial Outer Membrane Proteins*
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / immunology
  • Bacterial Proteins / metabolism*
  • Carrier Proteins / chemistry
  • Carrier Proteins / immunology
  • Carrier Proteins / metabolism*
  • Cysteine Endopeptidases / metabolism*
  • Humans
  • Immunoglobulin G / immunology
  • Immunoglobulin G / metabolism*
  • Molecular Sequence Data
  • Molecular Weight
  • Recombinant Proteins / immunology
  • Recombinant Proteins / metabolism
  • Streptococcus pyogenes / enzymology*
  • Streptococcus pyogenes / immunology


  • Antigens, Bacterial
  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • Carrier Proteins
  • Immunoglobulin G
  • Recombinant Proteins
  • streptococcal M protein
  • Cysteine Endopeptidases
  • streptopain