Abstract
RNase P derived from S. cerevisiae nuclei was tested for its ability to cleave a variety of naturally occurring and selectively altered precursor-tRNA molecules to yield matured 5' termini. Precursors were synthesized in vitro in order to test which aspects of substrate structure are crucial to recognition and cleavage by RNase P. Base modifications in the precursor substrates are not required for cleavage by the enzyme, but deletion and substitution mutations affecting any portion of the precursor tertiary structure reduce cleavage. In particular, a number of alterations in the intervening sequence (IVS) reduce the susceptibility of the substrate to cleavage by RNase P. The significance of these results is discussed in reference to the contribution of the IVS to the structure of the precursor-tRNA.