کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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5917453 | 1570734 | 2011 | 9 صفحه PDF | دانلود رایگان |

IdeS (IgG-degrading enzyme of Streptococcus pyogenes) is a virulence factor for S. pyogenes, group A Streptococcus (GAS). IdeS is believed to allow GAS to evade antibody-mediated phagocytosis by cleaving IgG at the lower hinge region. Human immunoglobulins bind to the GAS surface by two mechanisms: Specific antibodies attach at the Fab region to their specific antigens on the bacterial surface. Immunoglobulins can also attach nonspecifically at the Fc region to streptococcal M and M-like proteins. This phenomenon is believed to form the host-like coat and to block the recognition of Fc region by Fc receptor on phagocytes and antibody-dependent cell-mediated cytotoxicity. It is not known whether IdeS preferentially cleaves IgG attached at the Fab or Fc regions. To explore this issue, we used Sepharose beads coated with protein A or L or M protein as surrogate markers for specific (Fab) and nonspecific (Fc) binding sites. We found that IdeS cleaved Fab-bound IgG as rapidly as soluble IgG. In contrast, Fc-bound IgG was cleaved about 4 fold less than soluble IgG. In a competitive binding assay, we found that M protein had a greater affinity than IdeS to attach to the Fc region of human IgG. Thus, IdeS exhibited preferential IgG endopeptidase activity for Fab-bound IgG while allowing the non-specific binding of IgG to remain attached to M protein. We propose that this preferential enzymatic activity accounts for the ability of GAS to resist immunoglobulin-mediated phagocytosis and cytotoxicity.
⺠IdeS cleaved Fab-bound IgG as rapidly as soluble IgG. ⺠Fc-bound IgG was cleaved about 4 fold less than soluble IgG. ⺠M protein had a greater affinity than IdeS to attach to the Fc region of human IgG. ⺠IdeS exhibited preferential IgG endopeptidase activity for Fab-bound IgG while allowing the non-specific binding of IgG to remain attached to M protein. ⺠This preferential enzymatic activity accounts for the ability of GAS to resist immunoglobulin-mediated phagocytosis.
Journal: Molecular Immunology - Volume 49, Issues 1â2, OctoberâNovember 2011, Pages 134-142