Presence of an intron in elongator methionine-tRNA of Halobacterium volcanii.

The gene for the elongator (internal) methionine transfer RNA (tRNA(mMet)) in the archaebacterium Halobacterium volcanii contains a 75 base pair intron (intervening sequence) and lacks the 3'-terminal CCA sequence of the mature tRNA. There is a single copy of this gene in the genome and it is expressed. Northern hybridization experiments indicate that the precursor is processed to produce mature tRNA and a free intron species. A secondary structure of the transcript can be formed in which the anticodon stem of the tRNA is extended. Two symmetrically placed three-base bulge loops separated by a 4 base pair stem are present in this extension. The cleavage sites for the removal of the intron are placed between the middle and 3' residues of these loops.