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  • Title: A second divalent metal ion in the group II intron reaction center.
    Author: Gordon PM, Fong R, Piccirilli JA.
    Journal: Chem Biol; 2007 Jun; 14(6):607-12. PubMed ID: 17584608.
    Abstract:
    Group II introns are mobile genetic elements that have been implicated as agents of genetic diversity, and serve as important model systems for investigating RNA catalysis and pre-mRNA splicing. In the absence of an atomic-resolution structure of the intron, detailed understanding of its catalytic mechanism has remained elusive. Previous identification of a divalent metal ion stabilizing the leaving group in both splicing steps suggested that the group II intron may employ a "two-metal ion" mechanism, a catalytic strategy used by a number of protein phosphoester transfer enzymes. Using metal rescue experiments, we now reveal the presence of a second metal ion required for nucleophile activation in the exon-ligation step of group II intron splicing. Coupled with biochemical and structural evidence of at least two metal ions at the group I intron reaction center, these results suggest a mechanistic paradigm for describing catalysis by large ribozymes.
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