Isolation and Properties of tRNA Nucleotidyl Transferase from Yeast

tRNA nucleotidyl transferase has been purified 5000‐fold from commercial bakers' yeast. The isolation procedure includes ammonium sulfate fractionation and chromatography on DEAE‐cellulose, CM‐cellulose, Biogel and phosphocellulose. The enzyme is homogeneous on analytical centrifugation and by sodium dodecylsulfate gel electrophoresis. The molecular weight of the native and denatured enzyme M c=O r is 71000 as determined by ultracentrifuge measurements and 70000 as determined by sodium dodecylsulfate gel electrophoresis. On micro isoelectric focusing the enzyme shows an isoelectric point at about pH 7.5. The enzyme catalyses the incorporation of ATP and CTP into the 3′‐end of tRNA, and, in the presence of pyrophosphate, the pyrophosphorolyses of adenylic and cytidylic acid residues from the 3′‐end of tRNA.