title: Effect of magnesium ion on the structure of the 5S RNA from Escherichia coli. An imino proton magnetic resonance study of the helix I, IV, and V regions of the molecule.
abstract: The imino proton nuclear magnetic resonance spectrum of Escherichia coli 5S ribonucleic acid (RNA) changes when the Mg2+ ion concentration drops below physiological levels. The transition between the physiological and low magnesium spectral forms of 5S RNA has a midpoint at approximately 0.3 mM Mg2+. Many of the most conspicuous changes observed in the downfield spectrum of 5S RNA as the magnesium concentration is reduced are due to adjustments in the structures of helices I and IV and the disappearance of resonances originating in helix V. The binding of ribosomal protein L25 to 5S RNA in the absence of magnesium stabilizes helix V structures.
mesh_terms: D001483:Base Sequence; D004926:Escherichia coli / Q000378:metabolism*; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D009690:Nucleic Acid Conformation; D012335:RNA, Ribosomal / Q000187:drug effects* / Q000378:metabolism; D013816:Thermodynamics
chemical_list: D012335:RNA, Ribosomal; D008274:Magnesium