2 items with the tag “magnesium

  • Resurrection of an Ancestral Peptidyl Transferase
    NAI 2013 Georgia Institute of Technology Annual Report

    Ancient components of the ribosome, inferred from a consensus of previous work, were constructed in silico, in vitro, and in vivo. The resulting model of the ancestral ribosome incorporates about 20% of the extant 23S rRNA and fragments of four ribosomal proteins. We confirmed that the ancestral rRNA can: (i) assume canonical 23S rRNA-like secondary structure, (ii) assume canonical tertiary structure, and (iii) form native complexes with ribosomal protein fragments. We call the assembled a-RNA and rPeptide fragments the aPTC. We are currently focusing on characterizing the catalytic activity of the a-PTC.

    ROADMAP OBJECTIVES: 3.2 4.2
  • Ironing Out the RNA World
    NAI 2013 Georgia Institute of Technology Annual Report

    We have proposed hypothesize that Fe2+ was an RNA cofactor on the ancient earth when iron was benign and abundant, and that Fe2+ was replaced by Mg2+ during the great oxidation. Our hypothesis is supported by our observations (1,2) that (i) RNA folding is conserved between complexes with Fe2+ and Mg2+ and (ii) at least some phosphoryl transfer ribozymes are more active in the presence of Fe2+ than Mg2+. We have shown that reversing the putative metal substitution in an anoxic environment, by removing Mg2+ and adding Fe2+, expands the catalytic repertoire of some RNAs. Fe2+ can confer on RNA a previously uncharacterized ability to catalyze single electron transfer. Catalysis is specific, in that it is dependent on the type of RNA. The 23S rRNA and tRNA, some of the most abundant and ancient RNAs (3), are found to be efficient electron transfer ribozymes in the presence of Fe2+. Therefore, the catalytic competence of ancient RNAs may have been greater in early earth conditions than in extant conditions, and the experiments described here may be reviving latent function. The Center is currently testing the hypothesis that replacement of Fe2+ by Mg2+ in RNA assemblies has not been universal.

    ROADMAP OBJECTIVES: 4.1 4.2