The LAGLIDADG Homing Endonuclease Family

The LAGLIDADG protein family includes the first identified and biochemically characterized intron-encoded proteins (Dujon 1980; Lazowska et al. 1980; Jacquier and Dujon 1985), as described in this volume by Dujon. It has been variously termed the ‘DOD’, ‘dodecapeptide’, ‘dodecamer’, and ‘decapeptide’ endonuclease family, based on the conservation of a ten-residue sequence motif (Dujon 1989; Dujon et al. 1989; Belfort et al. 1995; Belfort and Roberts 1997; Dalgaard et al. 1997; Chevalier and Stoddard 2001). The LAGLIDADG endonucleases are the most diverse of the homing endonuclease families. Their host range includes the genomes of plant and algal chloroplasts, fungal and protozoan mitochondria, bacteria and Archaea (Dalgaard et al. 1997). One reason for the wide phylogenetic distribution of LAGLIDADG genes appears to be their remarkable ability to invade unrelated types of intervening sequences, including group I introns, archaeal introns and inteins (Belfort and Roberts 1997; Chevalier and Stoddard 2001). Descendents of LAGLIDADG homing endonucleases also include the yeast HO mating type switch endonuclease (Jin et al. 1997), which is encoded by an independent reading frame rather than within an intron, but does carry remnants of an inactive intein domain (Haber and Wolfe, this Vol.), and maturases that assist in RNA splicing (Delahodde et al. 1989; Lazowska et al. 1989; Schafer et al. 1994; Geese and Waring 2001; Caprara and Waring, this Vol.).