δ-Crystallin is a soluble structural protein that is recruited from argininosuccinate lyase through gene sharing to confer special refractive properties in avian eye lenses. The present study investigates the role of Glu367. This residue is located in the interface of the double dimer. Mutation in Glu367 caused no subtle changes in the conformation and stability of the secondary and tertiary structure as compared to wild-type protein. However, dissociated dimeric form was observed for E367A mutant protein. The dissociated dimers were unstable and prone to form protein aggregates. These results indicate that the interactions provided by E367 in the dimer-dimer interface of δ-crystallin are important for double dimmer assembly.