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Nonenzymatic hydrolysis of RNA: Pb(II)‐catalyzed site specific hydrolysis of transfer RNA. The role of the tertiary folding of the polynucleotide chain
Author(s) -
Sundaralingam Muttaiya,
Rubin John R.,
Can John F.
Publication year - 1984
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560260736
Subject(s) - phosphodiester bond , chemistry , cleavage (geology) , transfer rna , rna , stereochemistry , polynucleotide , hydrolysis , nucleotide , nucleophile , ribonucleotide , catalysis , biochemistry , biology , paleontology , fracture (geology) , gene
Pb 2+ specifically cleaves yeast tRNA Phe in orthorhombic crystals at phosphates P18 and P60 in the dihydrouridine (D) and pseudouridine (T) loops, respectively. Although there are three major lead binding sites in the tRNA, it appears that both cleavages are affected by the same lead ion. The P18 site is apparently the same site that is hydrolyzed by Pb 2+ in solutions of the tRNA and is the major cleavage site in crystals. It is shown from P 32 labeling studies with polynucleotide kinase that the products of Pb 2+ cleavage have the 5′‐hydroxyls on G18 and C60, and consequently the 3′ phosphates are on D17 and U59. The OH − in the first coordination sphere of the hydroxo complex Pb(OH) + either directly or through a water molecule abstracts the proton of the 2′‐OH of D17. This promotes a nucleophilic attack by 2′‐O − on P18 with subsequent cleavage of the PO5′ ester bond to generate the major Pb 2+ cleavage product pG18‐A76. The anchoring of the Pb 2+ by the T‐loop and D‐loop residues seemingly provide the right environment for the generation of the hydroxo complex required for the hydrolysis. Additionally the strain of the phosphodiester conformation at P18 enhances the cleavage at that site. The Pb 2+ ‐catalyzed cleavage of tRNA exemplifies a mechanism used not only for the hydrolysis of transfer RNA but one potentially used by other RNA‐catalyzed reaction utilizing metal ion cofactors.