Properties of H-volcanii tRNA intron endonuclease reveal a relationship between the archaeal and eucaryal tRNA intron processing systems

To better understand the relationship between archaeal and eucaryal tRNA introns and their processing systems, we have cloned the gene encoding the tRNA intron endonucleases from the archaeon H. volcanii. The gene encodes a 37 kDa protein that appears to be present as a homodimer under native conditions. Recombinant forms of this protein were expressed in E. coli and found to cleave precursor tRNAs lacking full mature tRNA structure, a property observed for the native endonuclease. Comparative sequence analysis revealed that similar proteins existed in other Archaea and that these proteins have significant similarity with two subunits of the yeast tRNA intron endonuclease. These results provide evidence that the archaeal and eucaryal tRNA intron processing systems are related and suggest a common origin for tRNA introns in these organisms.