Comparison of mitochondrial and cytosolic tRNA nucleotidyltransferases from Triticum aestivum

Abstract

Here we report the partial purification and characterization of wheat mitochondrial ATP (CTP):tRNA nucleotidyltransferase (EC 2.7.7.25). Our purification scheme involves ammonium sulfate fractionation and chromatography on anion-exchange, hydroxyapatite, and affinity columns. Our results indicate that the enzyme is stable over a broad range of temperatures with highest activity at 37°C. High activity is seen at alkaline pH with a maximum at pH 9. The enzyme exhibits maximal activity in the presence of 10 mM MgCl2 and is inhibited by (at least) 100 mM NaCl. We also show that a second form of this enzyme exists in the wheat cytosolic fraction. This enzyme shares many features with the mitochondrial enzyme but differs from the mitochondrial enzyme in its elution profile from hydroxyapatite and in its response to manganese.Key words: tRNA nucleotidyltransferase, wheat, mitochondria.