Published online by Cambridge University Press: 06 September 2002
A novel mechanism for the very first step in polypeptide elongation on the ribosome has recently been proposed by Simonson and Lake (2002). According to their transorientation hypothesis, the incoming aminoacyl-transfer RNA (aa-tRNA) initially binds to the messenger RNA (mRNA) with the anticodon stacked on the 5′ side of the anticodon loop; then, following GTP hydrolysis, the tRNA swings into the A-site by switching from the 5′-stacked conformation to the classic 3′-stacked geometry while maintaining Watson–Crick base pairing with the mRNA. There are several serious problems with this proposal.