WHY DO 2 EF-TU MOLECULES ACT IN THE ELONGATION CYCLE OF PROTEIN-BIOSYNTHESIS

In the elongation cycle of bacterial protein biosynthesis, the binding of aminoacyl-tRNA (aa-tRNA) to the A-site of mRNA-programmed ribosome s is mediated by elongation factor Tu (EF-Tu) and associated with the hydrolysis of GTP. Recently, in the case of cognate aa-tRNA, the parti cipation of two GTP molecules has been implicated in this reaction. Th ese are likely to be involved in preventing the indiscriminate binding of aa-tRNA to the ribosomal A-site. This article integrates this unex pected finding with our current knowledge of the structure-function re lationships of the macromolecules involved in the elongation cycle.