Chemical evidence for a codon-induced allosteric change in tRNALys involving the 7-methylguanosine residue 46.
[32P]TRNALys, from Escherichia coli, was modified with kethoxal, in the presence and absence of the oligonucleotide codon (A)4. The presence of the codon resulted in a faster modification rate of the tRNA at three guanine sites which were identified by a diagonal fingerprint method. A large increase in the modification rate occurred at the 7-methylguanosine residue 46 (m7G-46) in the presence of the codon: weakly enhanced modification was observed at G-15 and G-57. It is concluded that the formation of a codon-anticodon complex induces, primarily, a conformational change involving disruption of the m7G-46 from the m7G-46 . G-22 . C-13 base triple. Subsequently, the guanines of G-15 and G-57, in the D and T loops, respectively, become slightly more reactive, suggesting a weak tendency for these two interacting arms to unfold. The results are interpreted in terms of an equilibrium between two main conformers, and a third minor one; the possible significance of these conformers in protein biosynthesis, is considered.
D001483:Base Sequence; D003062:Codon; D004926:Escherichia coli / Q000032:analysis; D006151:Guanosine / Q000031:analogs & derivatives*; D008239:Lysine; D009690:Nucleic Acid Conformation; D012333:RNA, Messenger; D012343:RNA, Transfer; D006163:Ribonuclease T1
D003062:Codon; D012333:RNA, Messenger; D006151:Guanosine; C016578:7-methylguanosine; D012343:RNA, Transfer; D006163:Ribonuclease T1; D008239:Lysine