While genome recoding using quadruplet codons to incorporate non-proteinogenic amino acids is attractive for biotechnology and bioengineering purposes, the mechanism through which such codons are translated is poorly understood. Here we investigate translation of quadruplet codons by a +1-frameshifting tRNA, SufB2, that contains an extra nucleotide in its anticodon loop. Natural post-transcriptional modification of SufB2 in cells prevents it from frameshifting using a quadruplet-pairing mechanism such that it preferentially employs a triplet-slippage mechanism. We show that SufB2 uses triplet anticodon-codon pairing in the 0-frame to initially decode the quadruplet codon, but subsequently shifts to the +1-frame during tRNA-mRNA translocation. SufB2 frameshifting involves perturbation of an essential ribosome conformational change that facilitates tRNA-mRNA movements at a late stage of the translocation reaction. Our results provide a molecular mechanism for SufB2-induced +1 frameshifting and suggest that engineering of a specific ribosome conformational change can improve the efficiency of genome recoding.
Gamper, Howard; Li, Haixing; Masuda, Isao; Miklos Robkis, D.; Christian, Thomas; Conn, Adam B.; Blaha, Gregor; Petersson, E. James; Gonzalez, Ruben L.; and Hou, Ya-Ming, "Insights into genome recoding from the mechanism of a classic +1-frameshifting tRNA." (2021). Department of Biochemistry and Molecular Biology Faculty Papers. Paper 177.
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