In nature, hairpin ribozymes are found in the satellite RNA of tobacco ringspot virus where they mediate self-cleavage and ligation reactions that are needed for satellite RNA replication. Hairpin ribozymes consist of two essential helix-loop-helix elements that must dock into a noncoaxial tertiary structure that brings loop nucleotides into proximity to create the active site. The two essential elements can be joined by an unstructured linker in the minimal ribozyme (2WJ) or by a 4-way helical junction (4WJ). A 4-way junction stabilizes the functional docked structure. Arrows indicate the phosphodiester bond in loop A that undergoes reversible cleavage.