Elongation factor 1-delta (EF-1delta) is one of four subunits of the elongation factor-1 complex, a non-ribosomal complex that is involved in delivery of aminoacyl tRNAs to the ribosome. EF-1 is composed of EF-1alpha, EF-1beta, EF-1delta, and EF-1gamma. EF-1beta and EF-delta function as guanine nucleotide exchange factors and stimulate the exchange of GDP bound to EF-1 alpha for GTP.