High-resolution crystal structures of large ribosomal subunits from Deinococcus radioduranscomplexed with tRNA-mimics indicate that precise substrate positioning, mandatory for efficient protein biosynthesis with no further conformational rearrangements, is governed by remote interactions of the tRNA helical features. Based on the peptidyl transferase center (PTC) architecture, on the placement of tRNA mimics, and on the existence of a two-fold related region consisting of about 180 nucleotides of the 23S RNA, we proposed a unified mechanism integra-ting peptide bond formation, A-to-P site translocation, and the entrance of the nascent protein into its exit tunnel. .
