A protein complex required for the splicing of intron 4 of the cytochrome b (COB) gene. In S. cerevisiae, the complex contains the maturase bI4 (which derives from one of the products of the splicing), Leucyl-tRNA synthetase NAM2 and the intron 4 of the cytochrome b pre-mRNA. The two proteins stimulate the ribozyme activity of the pre-mRNA which autoctalyse a group I intron splicing.
bI4 intron splicing complex