Structural determination of Streptococcus pyogenes M1 protein interactions with human immunoglobulin G using integrative structural biology
Fig 2
M1 interactions with IgG subclasses.
(a) The model for M1 (A- and S-domains)-IgG1 full length non-immune Fc-mediated interaction. Important domains of the M1 protein are shown, where A- and S-domains play a crucial role. The molecular details of the Fc-binding site are shown in panel (b) where inter- and intra-XLs are mapped on the protein complex. (b-e) The S-domain of the M1-protein interacts with the Fc-region of IgG1-4. All models are generated by the TX-MS workflow based on cross-link constraints derived from MS data. Intra-XLs for each IgG are shown in cyan, while inter-XLs between the two proteins are in blue. The binding interfaces of the M1 protein on the Fc-domain of all IgG subclasses are similar and mediated via the CH3 domains. This region is involved in binding to IgG Fc-receptors (FcγR), predicted to be inhibited by the M1 protein interaction.