A Relaxed Active Site After Exon Ligation by the Group I Intron

Journal Article · Tue Jan 01 04:00:00 EST 2008 · Proceedings of the National Academy of Sciences of the USA

DOI:https://doi.org/10.1073/pnas.0712016105· OSTI ID:959471

Lipchock, S; Strobel, S

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 no direct exonic interactions and even in the absence of the scissile phosphate, two metal ions remain bound within the active site. Together, these data suggest that release of the ligated exons from the intron is preceded by a change in substrate-metal coordination before tertiary hydrogen bonding contacts to the exons are broken.

• Research Organization: Brookhaven National Laboratory (BNL) National Synchrotron Light Source
• Sponsoring Organization: Doe - Office Of Science
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 959471
• Report Number(s): BNL--82457-2009-JA
• Journal Information: Proceedings of the National Academy of Sciences of the USA, Journal Name: Proceedings of the National Academy of Sciences of the USA Journal Issue: 15 Vol. 105; ISSN 0027-8424; ISSN PNASA6
• Country of Publication: United States
• Language: English

Related Subjects

08 HYDROGEN
36 MATERIALS SCIENCE
BONDING
CRYSTAL STRUCTURE
EXONS
GROUND STATES
HYDROGEN
INTRONS
KINETICS
PHOSPHATES
RNA
SPLICING
THERMODYNAMICS
national synchrotron light source