title: Quantitative aspects of metal ion binding to certain transfer RNA anticodon loop modified nucleosides.
abstract: Magnesium and manganese ions bind strongly to the unusual transfer RNA anticodon loop nucleotides, N-[(9-beta-D-ribofuranosyl-9H-purin-6-yl)carbamoyl]-L-threonine 5'-monophosphate (pt6A) and uridine-5-oxyacetic acid 5'-monophosphate (pV). Potentiometric measurements have shown that the delta G for metal ion-pt6A complex formation is 2-3-times more exothermic than for AMP. Electron-nuclear longitudinal dipolar relaxation data yielded manganese-ligand atom distances which permit a three-dimensional construct of the complex in which metal is coordinated to the phosphate, carboxylate of the threonine side-chain (with the nucleotide in the anti glycosidic conformation) and N7 of the adenine ring. Similarly, manganese binds strongly to pV, involving phosphate and carboxylate functions. It is possible that a facet of the functional role of these unusual residues is to chelate magnesium ions and in so doing permit optimum anticodon loop conformational stability and stability of tRNA-mRNA-ribosome complexes.
mesh_terms: D000926:Anticodon; D004578:Electron Spin Resonance Spectroscopy; D008274:Magnesium; D008345:Manganese; D011199:Potentiometry; D011685:Purine Nucleotides; D012343:RNA, Transfer; D013816:Thermodynamics; D014542:Uridine Monophosphate / Q000031:analogs & derivatives
chemical_list: D000926:Anticodon; D011685:Purine Nucleotides; D008345:Manganese; C009114:N-(purine-6-ylcarbamoyl)-L-threonine ribonucleoside 5'-phosphate; C043679:uridine-5-oxyacetic acid 5'-monophosphate; D012343:RNA, Transfer; D014542:Uridine Monophosphate; D008274:Magnesium