Group II introns are large, multidomain ribozymes that catalyze cleavage and ligation of both RNA and DNA.   These ancient RNA molecules share structural features with spliceosomal RNAs and are therefore believed to be evolutionary predecessors of the eukaryotic spliceosome.   The structural organization and folding pathways of group II introns has recently been elucidated through crystallographic and kinetic analyses, revealing a network of conserved tertiary interactions and junction motifs that control formation of the active-site scaffolding.  Detailed crystallographic analyses of multiple splicing steps, in the presence of monovalent and divalent anomalous scattering ions, reveals that ribozyme chemistry is potentiated through the action of a four-metal ion center that contains two obligate magnesium and two obligate potassium ions.  This work has shown that monovalent ions can bind with high specificity to RNA sites, where they form specific metal clusters with magnesium ions and play key roles in potentiating catalysis.

Metal clusters in RNA chemistry:  Familiar themes, but a different cast of characters in metal ion catalysis by group II introns

245th National Meeting (2013)

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