The receptor for branch-site docking within a group II intron active site.
The distinguishing feature of group II introns, and the property that links them with spliceosomal catalysis, is their ability to undergo splicing through branching. In this reaction, the 2'-hydroxyl group of a specific adenosine within intron domain 6 serves as the nucleophile for attack on the 5' splice site. We know less about branching than any other feature of group II intron catalysis, largely because the receptor structure for activating the branch site is unknown. Here, we identify the intronic region that binds the branch site of a group IIB intron. Located in domain 1, close to receptors for intron domain 5 and both splice sites, we demonstrate that the branch-site receptor is a functional element required for transesterification. Furthermore, we show that crosslinked branch sites can carry out both steps of splicing, suggesting that the conformational state of the intron core is set early and that it persists throughout the entire splicing process.
Hamill
Stephanie
S
Integrated Program in Cellular, Molecular and Biophysical Studies, Columbia University, 500 West 168th Street, New York, New York 10032, USA.
Pyle
Anna Marie
AM
D001665:Binding Sites; D002874:Chromosome Mapping; D007438:Introns / Q000235:genetics / Q000502:physiology*; D008274:Magnesium / Q000502:physiology; D009690:Nucleic Acid Conformation; D022821:RNA Splice Sites; D012326:RNA Splicing / Q000502:physiology*; D017423:Sequence Analysis, RNA
D022821:RNA Splice Sites; D008274:Magnesium