Structural determination of Streptococcus pyogenes M1 protein interactions with human immunoglobulin G using integrative structural biology
Fig 1
The schematic view of the studied system.
(a) Electron microscopy image of the surface of bacteria representing the length of M1 protein. The scale bar in the larger image is 500 nm where in the zoom view below is 100 nm. Small arrows indicate the position of M1 proteins. (b) The general structure of human IgG. (c) Important domains of the M1 protein, including the hypervariable domain (A), fibrinogen binding domains (B1/B2), S-region, and albumin-binding domains (C1/C2/C3). The coiled-coil region, the anchor, and the signal peptide are shown to the right specifying by the residue numbers in red. (d) IgG-orientations and -interactions with the M1-protein on the surface of GAS. Three major interactions are shown, including Fc- and Fab-mediated interactions, as well as opsonizing antibodies bound to the surface of the bacteria [16]. M1 is shown in gray while IgGs are in pink. The peptidoglycan layer on the surface of bacteria is shown in green.