EF1B, also known as EEF1B2, is a translation elongation factor. It belongs to the EF-1-beta/EF-1-delta family. Elongation factors are a set of proteins that are used in protein synthesis in the cell. In the ribosome, they facilitate translational elongation, from the formation of the first peptide bond to the formation of the last one. EF1B is more complex in eukaryotes than in bacteria, and consists of three subunits: EF1B-alpha, EF1B-gamma and EF1B-beta. EF1B contains 1 GST C-terminal domain. It is involved in the transfer of aminoacylated tRNAs to the ribosome. EF1B is required to regenerate EF1A from its inactive form (EF1A-GDP) to its active form (EF1A-GTP). EF1A is then ready to interact with a new aminoacyl-tRNA to begin the cycle again.