Identification of a 100‐kDa protein associated with nuclear ribonuclease P activity in Schizosaccharomyces pombe

Ribonuclease P from the fission yeast Schizosaccharomyces pombe has been purified to apparent homogeneity. A purification of 23,000-fold was achieved by four fractionation steps with DEAE-cellulose chromatography, phosphocellulose chromatography, glycerol-gradient fractionation and finally tRNA-affinity chromatography. A 100-kDa protein was present in the most pure preparations in amounts approximately stoichiometric with the previously identified RNA components of the enzyme, K1-RNA and K2-RNA [Krupp, G., Cherayil, B., Frendeway, D., Nishikawa, S. & Söll, D. (1986) EMBO J. 5, 1697-1703]. A cross-linking experiment utilizing a 4-thiouridine-substituted precursor tRNA demonstrated that the 100-kDa protein interacts with the ribonuclease P substrate in a specific fashion. We therefore conclude that the protein component of S. pombe ribonuclease P is a 100-kDa protein.