Two tRNA-binding sites in addition to A and P sites on eukaryotic ribosomes.
The interaction of tRNA with 80 S ribosomes from rabbit liver was studied using biochemical as well as fluorescence techniques. Besides the canonical A and P sites, two additional sites were found which specifically bind deacylated tRNA. One of the sites is analogous to the E site of prokaryotic ribosomes, in that binding of tRNA is labile, does not depend on codon-anticodon interaction, does not protect the anticodon loop from solvent access, and requires the presence of the 3'-terminal adenosine of the tRNA. In contrast, the stability of the tRNA complex with the second site (S site) is high. tRNA binding to the S site is also codon-independent; nevertheless, the anticodon loop is shielded from solvent access. Removal of the 3'-terminal adenosine decreases the affinity of tRNA(Phe) for the S site approximately 50-fold. tRNA(Phe) is retained at the S site during translocation and through poly(Phe) synthesis. Thus, the S site does not seem to be an intermediate site for the tRNA during the elongation cycle. Rather, the tRNA bound to the S site may allosterically modulate the function of the ribosome.
Rodnina
M V
MV
Institut für Molekularbiologie Universität Witten/Herdecke, Germany.
Wintermeyer
W
W
D000818:Animals; D001665:Binding Sites; D001692:Biological Transport; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D011370:Proflavine / Q000378:metabolism; D012343:RNA, Transfer / Q000378:metabolism*; D012360:RNA, Transfer, Phe / Q000378:metabolism; D011817:Rabbits; D012270:Ribosomes / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
D012360:RNA, Transfer, Phe; D012343:RNA, Transfer; D011370:Proflavine