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  • Title: Magnesium is essential for formation of an active complex of a hammerhead ribozyme with its substrate: an investigation by NMR spectroscopy.
    Author: Orita M, Vinayak R, Andrus A, Takagi Y, Chiba A, Kaniwa H, Nishikawa F, Nishikawa S, Taira K.
    Journal: Nucleic Acids Symp Ser; 1995; (34):219-20. PubMed ID: 8841630.
    Abstract:
    The effects of magnesium ions on a 32-mer ribozyme (R32) were examined by high-resolution NMR spectroscopy. In solution, R32 (without its substrate) consisted of a GAAA loop, stem II, a non-Watson Crick three-base-paired duplex and a four-base-paired duplex that included a wobble base pair. When an uncleavable substrate RNA (RdC11) was added to R32 without Mg2+ ions, a complex did not form between R32 and RdC11 because the substrate-recognition regions of R32 formed intramolecular base pairs (the recognition arms were closed). By contrast, in the presence of Mg2+ ions, the R32-RdC11 complex was formed. Moreover, titration of mixtures of R32 and RdC11 with Mg2+ ions also induced the ribozyme-substrate interaction. These data suggest that Mg2+ ions are not only important as the true catalysts in the function of ribozyme-type metalloenzymes but they also induce the structural change in the R32 hammerhead ribozyme that is necessary for establishment of the active form of the ribozyme-substrate complex.
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