Plant tRNA suppressors: In vivo readthrough properties and nucleotide sequence of yellow lupin seeds tRNA

Transfer RNAs isolated from yellow lupin seeds were screened for tRNA dependent nonsense suppression in Xenopus laevis oocyte system. No opal (UGA) suppressor activity could be detected. However, a tRNA^Tyr isoacceptor species stimulates readthrough of the leaky UAG tobacco mosaic virus (TMV)-RNA stop codon. This natural suppressor tRNA was purified to homogeneity and its sequence was determined to be: pC---C---g--- A---C---C---U---U---A---m²G---c---U---C---A---G---D---G---Gm--- G---U---A---G---A---G---Cm₂²G---G---A---G---G---A---C---U---G--- ψ---A---m¹G---A---ψ---C---C---U---U---A---G---m⁷G---acp³U---C--- A---C---U---G---G---U---ψ---C---G---m¹A---A---Uz.sbnd;C---C---G--- G---U---A---G---G---U---C---G---G---A---C---C---A_OH. The GψA anticodon seqeunce, the presence of the modified nucleoside 3-(3-amino-3-carboxypropyl)uridine (acp³U) in the extra loo p and the absence of ribothymidine are of special interest.