Visualizing the solvent-inaccessible core of a group II intron ribozyme

Group II introns are well recognized for their remarkable catalytic capabil ities, but little is known about their three-dimensional structures. In ord er to obtain a global view of an active enzyme, hydroxyl radical cleavage w as used to define the solvent accessibility along the backbone of a ribozym e derived from group II intron ai5 gamma, These studies show that a highly homogeneous ribozyme population folds into a catalytically compact structur e with an extensively internalized catalytic core. In parallel, a model of the intron core was built based on known tertiary contacts. Although constr ucted independently of the footprinting data, the model implicates the same elements for involvement in the catalytic core of the intron.