Crystal structure of the tRNA 3′ processing endoribonuclease tRNase Z from Thermotoga maritima

The maturation of the tRNA 3 ' end is catalyzed by a tRNA 3 ' processing endoribonuclease named tRNase Z ( RNase Z or 3 '- tRNase) in eukaryotes, Archaea, and some bacteria. The tRNase Z generally cuts the 3 ' extra sequence from the precursor tRNA after the discriminator nucleotide. In contrast, Thermotoga maritima tRNase Z cleaves the precursor tRNA precisely after the CCA sequence. In this study, we determined the crystal structure of T. maritima tRNase Z at 2.6-angstrom resolution. The tRNase Z has a four- layer alpha beta/beta alpha sandwich fold, which is classified as a metallo- beta- lactamase fold, and forms a dimer. The active site is located at one edge of the beta- sandwich and is composed of conserved motifs. Based on the structure, we constructed a docking model with the tRNAs that suggests how tRNase Z may recognize the substrate tRNAs.