The bulged adenosine residue adopts a C3´-endo conformation that with the help of splicing factors Cwc25, Yju2 and Isy1 aligns a 2´ OH for an inline attack of a phosphorus atom at the 5´ splice site. Nucleophilic attack initiates the first of two successive transesterification reactions that splices out the intron—through an unusual 2´-5´-3´ linked lariat intermediate—where the second transesterification involves ligation of the two flanking exons.
The bulged adenosine residue assumes a C3´-endo conformation that, aided by splicing factors Cwc25, Yju2, and Isy1, positions a 2´ OH group for an inline attack by a phosphorus atom at the 5´ splice site. Nucleophilic attack initiates the first of two successive transesterification reactions that expel the intron—through an unusual 2´-5´-3´ linked lariat intermediate—where the second transesterification involves the joining of the two flanking exons.