Fc fragment of Immunoglobulins

The project was aimed at analysis of intermolecular interactions of Fc fragments with its nature or synthetic ligands to discover structural basis for effects leading to potential modification of immunoglobulin-containing medicaments (vaccines). We determined the structure of mouse immunoglobulin G2b what is the first structure of this isotype.

Fig. 1. Crystal structure of Fc-fragment of mouse IgG2b (PDB code 2RGS)

Fig. 2. Differences evoked various interactions within crystal lattice of IgG-Fc.

We found:

1. Most of IgG-Fc containing structures have distorted geometry of alpha-L-fucose, or incorrect alfa(6-1) glycosidic link.

2. Novel type of oligosaccharide-oligosaccharide interactions.

3. Intermolecular interactions with other molecules (e.g. ligands) play a major role in tertiary structure organisation (differences exceeding 15 Å).

4. CH2-CH3 interface (neonatal Fc receptor or G-protein binding site) binds glycosylation loop.