Solution structure of the loop B domain from the hairpin ribozyme

The hairpin ribozyme is a small catalytic RNA with a unique two-domain stru cture, Here we present the solution structure of the loop B domain of the h airpin ribozyme, which contains most of the catalytically essential nucleot ides, The 38-nucleotide domain contains a 16-nucleotide internal loop that forms one of the largest non-Watson-Crick segments of base pairing thus far determined by either NMR or crystallography, Since the solution structure of the smaller loop A domain has been previously solved, an NMR structure-b ased model of the 22,000 M-r hairpin ribozyme-substrate open complex emerge s by joining the two domain structures, Strikingly, catalytically essential functional groups for the loop B domain are concentrated within an expande d minor groove, presenting a dear docking surface for the loop A domain.