Endonuclease involved in intron homing (Probable). Recognizes DNA in the 23S rRNA gene intron (minimally 5'-CCGGGTAAGTTCCGG-3'), cutting after A-8 on the top and C-11 on the bottom strand. Has a slow turnover rate, cuts the coding strand with a slight preference over the non-coding strand (PubMed:9092657). Mn(2+), Co(2+) and Mg(2+) enable equal cleavage, Zn(2+) is less active and Ni(2+) is essentially inactive. Not extremely thermostable, has lost significant activity after 90 minues at 65 degreees Celsius, has no activity after 4 hours. Translated from a circularized intron.