Conformational Flexibility in the IgE-Fc3-4 Revealed in Multiple Crystal Forms

The structure of the IgE-Fc 3-4 has been solved in three new crystal forms, providing 13 snapshots of the Fc conformation and revealing a diverse range of open-closed motions among subunit chains and dimers. A more detailed analysis of the open-to-closed motion of the IgE-Fc 3-4 was possible with so many structures, and the new structures allow a more thorough examination of the flexibility of the IgE-Fc and its implications for receptor binding. The existence of hydrophobic pocket at the elbow region of the Fc appears to be conformation-dependent and suggests a means of regulating the IgE Fc conformation (and potentially receptor binding) with small molecules.