| A Ribozyme That Collaborates With Protein
Although group II introns are catalytic RNAs, they require the assistance of
proteins for efficient splicing in vivo. Proteins that facilitate splicing of organellar group II introns fall into two main
categories: intron-encoded maturases and host-encoded proteins. To function and proliferate within new environments, group II
introns often require assistance, which they obtain by recruiting or collaborating with proteins (Solem & Than et al, 2008).
In cases where the host derives a selective advantage from the presence of the intron, host proteins might help to
"domesticate" the RNA and put it to work in the cell. In all of these cases, the intron RNA tends to maintain a functional
ribozyme core and the actual chemistry of splicing and reverse-splicing are catalyzed by the RNA itself (Lambowitz & Zimmerly
2004). Recruited proteins are therefore likely to serve structural functions, assisting in the folding or stabilization of
active intron structures, or by forming regulatory complexes that link splicing with other metabolic pathways. There is have
been extensive studies on maturase proteins, which are encoded rather than recruited by group II introns (Lambowitz &
Zimmerly 2004). Maturases typically contain RNA binding motifs, DNA endonuclease motifs, and reverse-transcriptase motifs that
are essential for intron mobility (Belfort et al 2001; Pyle & Lambowitz, 2007). But there are also a diversity of host
proteins that are recruited and adapted to facilitate group II intron function. Some of the most interesting examples include
plant proteins that promote assembly and activity of group II introns in chloroplasts, and the DEAD-box motor proteins, such
as the yeast Mss116p, which facilitates splicing of the ai5γ group IIB intron (Solem & Than et al, 2008).