Figure 4

Schematic representation of group I intron splicing. The splicing pathway consists of two sequential transesterification reactions. The first reaction is initiated by the 3′–OH group of an exogenous GTP (αG) that docks into the G-binding pocket located in the P7 region and the 3′–OH group attacks the 5′ splice site. In the second reaction, the 3′–OH of the released 5′ exon attacks the phosphodiester bond between the intronic terminal G (ωG) and the 3′ exon, resulting in the liberation of the intron and the ligation of the exons.