second spliceosomal transesterification activity spliceosome conformational change to release U4 (or U4atac) and U1 (or U11) spliceosomal conformational changes to generate catalytic conformation obsolete 3'-splice site cleavage, exon ligation true biological_process GO:0006373 This term was made obsolete because it represents a molecular function. 3'-splice site cleavage, exon ligation OBSOLETE. (Was not defined before being made obsolete).