EF-1-beta and EF-1-delta stimulate the exchange of GDP bound to EF-1-alpha to GTP. EF-1 is composed of 4 subunits: alpha, beta, delta, and gamma. Causes an allergic reaction in human. Binds to IgE in 8% of 92 Taipei area patients suffering from bronchial asthma. Belongs to the EF-1-beta/EF-1-delta family.