CLEAVAGE SITE RECOGNITION BY THE TRANSFER-RNA 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, ne vertheless play a fundamental role in intron excision reaction. The el ements of the recognition set (invariant nt, nt at the cardinal positi ons) can contribute to the overall recognition process by providing ei ther a direct contact for the enzyme or by dictating the spatial orien tation of nt that are directly contacted.