Conditional Alternative Protein Splicing Promoted by Inteins from .

Protein splicing is a post-translational process by which an intervening protein, or an intein, catalyzes its own excision from flanking polypeptides, or exteins, coupled to extein ligation. Four inteins interrupt the MCM helicase of the halophile , two of which are mini-inteins that lack a homing endonuclease. Both inteins can be overexpressed in and purified as unspliced precursors; splicing can be induced by incubation with salt.