The C-terminal portion of the fibrinogen-binding protein of Streptococcus equi subsp. equi contains extensive α-helical coiled-coil structure and contributes to thermal stability

The major cell wall-associated protein of the equine pathogen Streptococcus equi subsp. equi is a fibrinogen-binding protein (FgBP) which binds horse fibrinogen and equine IgG-Fc avidly through residues located in the N-terminal half and central regions of the molecule, respectively. The molecule is a major virulence factor for the organism and displays protective potential. In the present study, we use circular dichroism spectroscopy to investigate the secondary structure of the protein and show through the analysis of a panel of recombinant FgBP truncates that the C-terminal portion of FgBP contains an extensive α-helical coiled-coil structure that contributes to the thermal stability of the molecule.