tRNA-isoleucine-tryptophan composite gene.

Transfer-RNA genes in archaea often have introns intervening between exon sequences. The structural motif at the boundary between exon and intron is the bulge-helix-bulge. Computational investigations of these boundary structures in Haloarcula marismortui lead us to propose that tRNA-isoleucine and tRNA-tryptophan genes are co-located.