Metal ion binding sites in a group II intron core

Group II introns are catalytic RNA molecules that require divalent metal io ns for folding, substrate binding, and chemical catalysis. Metal ion bindin g sites in the group II core have now been elucidated by monitoring the sit e-specific RNA hydrolysis patterns of bound ions such as Tb3+ and Mg2+. Maj or sites are localized near active site elements such as domain 5 and its s urrounding tertiary interaction partners. Numerous sites are also observed at intron substructures that are involved in binding and potentially activa ting the splice sites. These results highlight the locations of specific me tal ions that are likely to play a role in ribozyme catalysis.