Group II introns use intron-encoded reverse transcriptase, maturase and DNA endonuclease activities for site-specific insertion into DNA [2]. Although this type of intron is self splicing in vitro they require a maturase protein for splicing in vivo. It has been shown that a specific region of the aI2 intron is needed for the maturase function [1]. This region was found to be conserved in group II introns and called domain X [3].

1: Splicing defective mutants of the COXI gene of yeast mitochondrial DNA: initial definition of the maturase domain of the group II intron aI2. Moran JV, Mecklenburg KL, Sass P, Belcher SM, Mahnke D, Lewin A, Perlman P; Nucleic Acids Res 1994;22:2057-2064. PMID:8029012

2: Group II intron endonucleases use both RNA and protein subunits for recognition of specific sequences in double-stranded DNA. Guo H, Zimmerly S, Perlman PS, Lambowitz AM; EMBO J 1997;16:6835-6848. PMID:9362497

3: Evolutionary relationships among group II intron-encoded proteins and identification of a conserved domain that may be related to maturase function. Mohr G, Perlman PS, Lambowitz AM; Nucleic Acids Res 1993;21:4991-4997. PMID:8255751