Cleavage site recognition by the tRNA splicing endoribonuclease

A single tRNA-splicing endoribonuclease can cleave several precursors. In addition to the conserved nucleotides (nt), there are positions in the mature domain that, though not always occupied by the same nt, nevertheless play a fundamental role in intron excision reaction. The elements of the recognition set (invariant nt, nt at the cardinal positions) can contribute to the overall recognition process by providing either a direct contact for the enzyme or by dictating the spatial orientation of nt that are directly contacted.