Higher-order structure and thermal instability of bovine mitochondrial tRNASerUGA investigated by proton NMR spectroscopy

摘要: Abstract Although mammalian mitochondrial serine-specific tRNA with the anticodon UGA (tRNA Ser UGA) appears to possess an almost normal cloverleaf secondary structure, it exhibits extraordinarily low melting temperature ( t m ). An in vitro transcript without modified nucleosides had even lower and slightly less hyperchromicity, but its tertiary structure was apparently very similar that of native counterpart judging from aminoacylation activity body experimental evidence so far obtained for canonical tRNAs. The therefore used investigate higher-order thermal instability UGA. 1 H-NMR analysis showed takes a nearly L-shaped base-pairings those found yeast Phe , which is representative However, magnesium ion titration revealed Mg 2+ affected chemical shifts differently than tRNAs studied; former sensitive toward especially D-arm region. This observation confirmed by NMR paramagnetic manganese titration. Hill plots derived CD spectral changes caused suggested fewer binding sites as well transcript, finding consistent data. We thus surmise both itself originated reduction number divalent within molecule. These results suggest new type tRNA.