Catalysis of ribosomal translocation by sparsomycin

During protein synthesis, transfer RNAs (tRNAs) are translocated from the aminoacyl to peptidyl to exit sites of the ribosome, coupled to the movement of messenger RNA ( mRNA), in a reaction catalyzed by elongation factor G (EF-G) and guanosine triphosphate (GTP). Here, we show that the peptidyl transferase inhibitor sparsomycin triggers accurate translocation in vitro in the absence of EF-G and GTP. Our results provide evidence that translocation is a function inherent to the ribosome and that the energy to drive this process is stored in the tRNA-mRNA-ribosome complex after peptide-bond formation. These findings directly implicate the peptidyl transferase center of the 50S subunit in the mechanism of translocation, a process involving large-scale movement of tRNA and mRNA in the 30S subunit, some 70 angstroms away.