A Mn2(+)-dependent ribozyme.

An RNA hairpin identical in sequence with the one formed during autocyclization of the 414-nucleotide Tetrahymena intervening sequence undergoes strand scission at a specific site in the presence of Mn2+. In addition to representing one of the smallest and simplest ribozymes possible, strand scission occurs readily under physiological conditions, is unaffected by the presence of Mg2+, and displays salt, pH, and temperature optima of potential use in exploiting Mn2+ as a regulatory switch in intact cells. The chemistry of strand scission of the RNA hairpin is described, as is the Mn2(+)-dependent solvolysis of a 231-nucleotide RNA transcript containing this structural motif.