Sequence/structure selective thermal and photochemical cleavage of yeast-tRNAPhe by UO

The uranyl(VI) ion, UO, cleaves yeast tRNA^Phe both thermally and photochemically. Photochemical cleavage takes place at all positions but exhibits maxima at G₁₀, G₁₈, G₃₀, A₃₈, C₄₉ and A₆₂. Furthermore, in the presence of stoichiometric concentrations of citrate, the cleavage is generally suppressed except that strong cleavage at positions G₁₀ and C₄₈–U₅₀ persists, indicating the presence of a high-affinity metal-ion binding site. It is proposed that these photocleavage sites reflect the tertiary structure of the yeast tRNA^Phe molecule in terms of D-loop/T-loop interaction and anticodon loop conformation and that uranyl-mediated photocleavage of RNA may be used as a probe of RNA tertiary structure, and in particular for identifying binding sites for divalent metal ions. Thus a high-affinity metal-ion binding site is inferred in the Rcentral pocket' formed by the D-loop, the T-loop and the acceptor stem.