Ribonuclease P: an enzyme with an essential RNA component.

The activity of ribonuclease P on precursor tRNA substrates from Escherichia coli can be abolished by pretreatment of this enzyme with micrococcal nuclease or pancreatic ribonuclease A, as well as by proteases and by thermal denaturation. Highly purified RNase P exhibits one prominent RNA and one prominent polypeptide component when examined in polyacrylamide gels containing sodium dodecyl sulfate. The buoyant density in CsCl of RNase P, 1.71 g/ml, is characteristic of a protein-RNA complex. The activity of RNase P is inhibited by various RNA molecules. The presence of a discrete RNA component in RNase P appears to be essential for enzymatic function. A model is described for enzyme-substrate recognition in which this RNA component plays an important role.