Homing Endonuclease - Nomenclature

Nomenclature

Homing endonucleases are always indicated with a prefix that identifies their genomic origin, followed by a hyphen: "I-" for homing endonucleases encoded within an intron, "PI-" (for "protein insert") for those encoded within an intein. Some authors have proposed using the prefix "F-" ("freestanding") for viral enzymes and other natural enzymes not encoded by introns nor inteins, and "H-" ("hybrid") for enzymes synthesized in a laboratory. Next, a capital letter is derived from the first letter of the name of the genus of the natural source organism, and two lower case letters are derived from the name of the species of that organism. Finally, a roman numeral distinguishes different enzymes found in a the same organism.

For example, we can mention the enzyme PI-TliII that is the second enzyme encoded by an intein found in the archaea Thermococcus litoralis, and H-DreI, the first synthetic homing endonuclease, created in a laboratory from the enzymes I-DmoI and I-CreI, taken respectively from Desulfurococcus mobilis and Chlamydomonas reinhardtii.