EF-T

Binding of the incoming aminoacyl-tRNA requires a soluble supernatant factor, elongation factor T (EF-T) and GTP. EF-T is composed of two polypeptides: EF-Tu (heat unsteable) and EF-Ts (heat stable) EF-Tu is very abundant. Most aa-tRNAs in the cell are complexed with EF-Tu. EF-Tu does not react with fmet-tRNAmet explaining why this is not bound during elongation. When bound to EF-Tu the labile ester bond between the tRNA and aminoacyl residue is protected from hydrolysis.