A relaxed active site after exon ligation by the group I intron.

ABSTRACT: During RNA maturation, the group I intron promotes two sequential phosphorotransfer reactions resulting in exon ligation and intron release. Here, we report the crystal structure of the intron in complex with spliced exons and two additional structures that examine the role of active-site metal ions during the second step of RNA splicing. These structures reveal a relaxed active site, in which direct metal coordination by the exons is lost after ligation, while other tertiary interactions are retained between the exon and the intron. Consistent with these structural observations, kinetic and thermodynamic measurements show that the scissile phosphate makes direct contact with metals in the ground state before exon ligation and in the transition state, but not after exon ligation. Despite n

SUBMITTER: Lipchock SV 

PROVIDER: S-EPMC2311373 | biostudies-literature | 2008 Apr

REPOSITORIES: biostudies-literature