Figure 1.

Schematic illustration of the protein splicing process. The heavy lines, solid or hatched, symbolize polypeptide chains and the light dotted lines represent chain–chain interactions that stabilize the separate domains involved in protein splicing and homing endonuclease activity. The reactive nucleophilic groups at the splice junctions that participate in protein splicing are shown as thiols, as in the M. tuberculosis RecA intein, but could also be hydroxyls.