Crystallization and X-ray diffraction analysis of an all-RNA U39C mutant of the minimal hairpin ribozyme.

The hairpin ribozyme is a naturally occurring catalytic RNA composed of two helix-loop-helix domains, A and B, that dock to form the biologically active enzyme. Previously, the crystal structure of the hairpin has been solved as a four-way helical junction that incorporated the U1A protein as an artificial crystal-packing motif [Rupert & Ferré-D'Amaré (2001), Nature (London), 410, 780-786]. Here, the crystallization of a minimal junctionless hairpin ribozyme 64-mer is reported in the absence of protein. Crystals grow in space group P6(1)22, with unit-cell parameters a = 93.1, c = 123.2 A. Complete diffraction data have been collected to 3.35 A resolution. Structural analysis should provide details of intermolecular RNA docking, including the ground-state conformations of the U(39)C mutation relevant to hairpin catalysis.