Abstract
Leucyl-tRNA synthetase (LeuRS) is an essential RNA splicing factor for yeast mitochondrial introns. Intracellular experiments have suggested that it works in collaboration with a maturase that is encoded within the bI4 intron. RNA deletion mutants of the large bI4 intron were constructed to identify a competently folded intron for biochemical analysis. The minimized bI4 intron was active in RNA splicing and contrasts with previous proposals that the canonical core of the bI4 intron is deficient for catalysis. The activity of the minimized bI4 intron was enhanced in vitro by the presence of the bI4 maturase or LeuRS.