A LAGLIDADG homing endonuclease variant having novel substrate specificity, said variant being obtainable by a method comprising: (a) the mutation of at least one amino acid residue of the final C-terminal loop of a parent LAGLIDADG homing endonuclease, with the exclusion of the threonine 140 of I-CreI, b) the selection and/or screening of the variants from step (a) having a pattern of cleaved DNA targets that is different from that of the parent LAGLIDADG homing endonuclease.