(Science: biochemistry) peptidyltransferase components of ribosomes that catalyse formation of the acyl bond between the incoming amino acid residue and the peptide chain.
there are three classes of elongation factor: EF1- (EF tu in prokaryotes) binds gtp and aminoacyl trna, delivering it to the a site of ribosomes. EF 1- (EF Ts) helps in regeneration of gtp EF 1-. EF 2 (EF G) binds gtp and peptidyl trna and translocates it from the a site to the P site. Diptheria toxin inhibits protein synthesis in eukaryotes by adding an adp ribosyl group to a modified histidine residue (dipthamide) in elongation factor II.