EF-1 (elongation factor-1) is a multi-protein complex that is responsible for the delivery of aminoacyl-tRNAs to the ribosome. The EF-1 protein complex is composed of four subunits: EF-1 (alpha), EF-1 (beta), EF-1 (delta) and EF-1 (gamma). EF-1 (beta) is a 225 amino acid member of the EF-1 (beta)/EF-1 (delta) protein family and contains one GST C-terminal domain. Both EF-1 (beta) and EF-1 (delta) stimulate the exchange of GDP bound to EF-1 (alpha) to GTP. Phosphorylation of EF-1 (beta) affects the GDP/GTP exchange rate. Alternative splicing events of the gene that encodes EF-1 (beta) result in three transcript variants that differ only in the 5' UTR.