Principles of ion recognition in RNA: insights from the group II intron structures.
Metal ions promote both RNA folding and catalysis, thus being essential in stabilizing the structure and determining the function of large RNA molecules, including group II introns. The latter are self-splicing metalloribozymes, containing a heteronuclear four-metal-ion center within the active site. In addition to these catalytic ions, group II introns bind many other structural ions, including delocalized ions that bind the RNA diffusively and well-ordered ions that bind the RNA tightly with high occupancy. The latter ions, which can be studied by biophysical methods, have not yet been analyzed systematically. Here, we compare crystal structures of the group IIC intron from Oceanobacillus iheyensis and classify numerous site-bound ions, which are primarily localized in the intron core and near long-range tertiary contacts. Certain ion-binding sites resemble motifs observed in known RNA structures, while others are idiosyncratic to the group II intron. Particularly interesting are (1) ions proximal to the active site, which may participate in splicing together with the catalytic four-metal-ion center, (2) organic ions that bind regions predicted to interact with intron-encoded proteins, and (3) unusual monovalent ions bound to GU wobble pairs, GA mismatches, the S-turn, the tetraloop-receptor, and the T-loop. Our analysis extends the general principles by which ions participate in RNA structural organization and it will aid in the determination and interpretation of future RNA structures.
['Marcia|Marco|M|', 'Pyle|Anna Marie|AM|']
D056449:Bacillales D001665:Binding Sites D020134:Catalytic Domain D007438:Introns D008670:Metals D008958:Models, Molecular D009690:Nucleic Acid Conformation D011487:Protein Conformation D012326:RNA Splicing D012329:RNA, Bacterial D016337:RNA, Catalytic D016601:RNA-Binding Proteins
splicing tetraloop-receptor T-loop GA imino mismatch X-ray crystallography ribonucleoprotein