Mechanism for expanding the decoding capacity of transfer RNAs by modification of uridines.
One of the most prevalent base modifications involved in decoding is uridine 5-oxyacetic acid at the wobble position of tRNA. It has been known for several decades that this modification enables a single tRNA to decode all four codons in a degenerate codon box. We have determined structures of an anticodon stem-loop of tRNA(Val) containing the modified uridine with all four valine codons in the decoding site of the 30S ribosomal subunit. An intramolecular hydrogen bond involving the modification helps to prestructure the anticodon loop. We found unusual base pairs with the three noncomplementary codon bases, including a G.U base pair in standard Watson-Crick geometry, which presumably involves an enol form for the uridine. These structures suggest how a modification in the uridine at the wobble position can expand the decoding capability of a tRNA.
Weixlbaumer
Albert
A
Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK.
Murphy
Frank V
FV
Dziergowska
Agnieszka
A
Malkiewicz
Andrzej
A
Vendeix
Franck A P
FA
Agris
Paul F
PF
Ramakrishnan
V
V
D000595:Amino Acid Sequence; D000926:Anticodon / Q000235:genetics*; D020029:Base Pairing; D001483:Base Sequence; D003062:Codon / Q000235:genetics; D003461:Crystallography; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D012366:RNA, Transfer, Val / Q000235:genetics* / Q000502:physiology*; D014529:Uridine / Q000737:chemistry*
D000926:Anticodon; D003062:Codon; D012366:RNA, Transfer, Val; D014529:Uridine