Accurate translocation of mRNA by the ribosome requires a peptidyl group or its analog on the tRNA moving into the 30S P site.
The ribosome must accurately translocate mRNA to maintain the reading frame. Here, we monitor the position of mRNA within the ribosome before and after EF-G-catalyzed translocation near the initiation site. When a deacylated tRNA that is translocated to the 30S P site recognizes other nearby codons, movement of tRNA and mRNA often becomes uncoupled. Instead of moving in the 5' direction by 3 nucleotides, the mRNA slips backward, repositioning the tRNA on an out-of-frame codon more optimally spaced from the Shine-Dalgarno sequence. In contrast, when peptidyl-tRNA or its analog (N-acetyl-aminoacyl-tRNA) is translocated in the same context, translocation of mRNA is highly accurate. If aminoacyl-tRNA is translocated, an intermediate level of translocational accuracy is observed. Thus, translocational accuracy depends on the acylation state of the tRNA entering the 30S P site.
Fredrick
Kurt
K
Center for Molecular Biology of RNA, Sinsheimer Laboraties, University of California, Santa Cruz, Santa Cruz, CA 95064, USA.
Noller
Harry F
HF
D017123:Bacteriophage T7; D001483:Base Sequence; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D008969:Molecular Sequence Data; D020653:Peptide Elongation Factor G / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*; D016364:Reading Frames; D012270:Ribosomes / Q000378:metabolism*; D014764:Viral Proteins
D020653:Peptide Elongation Factor G; D012333:RNA, Messenger; D012346:RNA, Transfer, Amino Acyl; D014764:Viral Proteins; C019037:tRNA, peptidyl-; C062210:bacteriophage T7 RNA polymerase; D012321:DNA-Directed RNA Polymerases