Group II intron ribozymes are large catalytic RNA molecules, which have the ability to self-splicing. Thereby the non-coding introns are removed from the coding sequence
and the remaining exons are joined. The correct recognition of the splice site is ensured by pairing of two regions in the intron, the exon binding sites 1 and 2 (EBS1 and EBS2)
with the two intron binding sites (IBS1 and IBS2) located at the end of the 5'-exon. This thesis the solution structures of the 5'-splice site recognition complex in the absence and of the substrate of the group II intron Sc.ai5γ located in the cox1 gene of cerevisiae by NMR spectroscopy. Upon binding of IBS1, EBS1 adopts a conformation, which is stabilized by divalent metal ions. The influence of metal ions on structures were investigated by NMR and Circular Dichroism. The results provide a understanding of the relationship between three-dimensional structure and metalion at the atomic level.