InterPro domain: IPR036167

This entry represents a three-layer alpha/beta/alpha domain found as the catalytic domain at the C-terminal in homotetrameric tRNA-intron endonucleases [ 1 ], and as domains 2 and 4 (C-terminal) in the homodimeric enzymes [ 2 ]. tRNA-intron endonucleases ( 3.1.27.9 ) remove tRNA introns by cleaving pre-tRNA at the 5'- and 3'-splice sites to release the intron. The products are an intron and two tRNA half-molecules bearing 2',3' cyclic phosphate and 5'-hydroxyl termini [ 3 ]. These enzymes recognise a pseudosymmetric substrate in which two bulged loops of three bases are separated by a stem of four bp [ 4 ]. Although homotetrameric enzymes contain four active sites, only two participate in the cleavage, and should therefore, be considered as a dimer of dimers.

1. Crystal structure and evolution of a transfer RNA splicing enzyme. Science 280, 279-84
2. RNA recognition and cleavage by a splicing endonuclease. Science 312, 906-10
3. Properties of H. volcanii tRNA intron endonuclease reveal a relationship between the archaeal and eucaryal tRNA intron processing systems. Cell 89, 839-47
4. Structure determination of a truncated dimeric splicing endonuclease in pseudo-face-centered space group P2(1)2(1)2. Acta Crystallogr. D Biol. Crystallogr. 60, 447-52