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  • Title: Destabilization of the P site codon-anticodon helix results from movement of tRNA into the P/E hybrid state within the ribosome.
    Author: McGarry KG, Walker SE, Wang H, Fredrick K.
    Journal: Mol Cell; 2005 Nov 23; 20(4):613-22. PubMed ID: 16307924.
    Abstract:
    Retention of the reading frame in ribosomal complexes after single-round translocation depends on the acylation state of the tRNA. When tRNA lacking a peptidyl group is translocated to the P site, the mRNA slips to allow re-pairing of the tRNA with a nearby out-of-frame codon. Here, we show that this ribosomal activity results from movement of tRNA into the P/E hybrid state. Slippage of mRNA is suppressed by 3' truncation of the translocated tRNA, increased MgCl2 concentration, and mutation C2394A of the 50S E site, and each of these conditions inhibits P/E-state formation. Mutation G2252U of the 50S P site stimulates mRNA slippage, suggesting that decreased affinity of tRNA for the P/P state also destabilizes mRNA in the complex. The effects of G2252U are suppressed by C2394A, further implicating the P/E state in mRNA destabilization. This work uncovers a functional attribute of the P/E state crucial for understanding translation.
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