期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 105, 期 15, 页码 5699-5704出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0712016105
关键词
crystallography; metalloenzyme; ribozyme; splicing
资金
- NIGMS NIH HHS [GM022778, T32 GM008283, P01 GM022778] Funding Source: Medline
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.
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