The intrinsic flexibility of IgE and its role in binding Fc RI

The interaction between IgE and its high affinity cellular receptor (Fc RI) is an essential step in the development of allergic responses. Studies have identified the third constant domain of IgE (C 3) as the receptor binding region. The C 3 domain has unusual structural features; it was found to be a ‘molten globule’ structure in an isolated form, only assuming a well structured form upon binding to Fc RI. The conformational flexibility intrinsic to the receptor binding portion of the molecule may be useful to IgE in allowing the large allosteric changes postulated to be required for Fc RI engagement. If allosteric inhibitors can be developed then the dynamic properties of the C 3 domain may provide opportunities for therapeutic intervention in allergic disorders.