GO:0000386:   second spliceosomal transesterification activity
Catalysis of the second transesterification reaction of spliceosomal mRNA splicing. Ligation of the two exons occurs via a transesterification reaction where the free 3"-hydroxyl group of the 5" exon is the nucleophile attacking the 3" splice site. Non-expressed sequences are now detached from the exons. In cis splicing, the intron is in a lariat structure.