5'-Hydroxyl polyribonucleotide kinase from HeLa cell nuclei.  Purification and properties. 
An enzyme, 5'-hydroxyl polyribonucleotide kinase, which catalyzes the phosphorylation of 5'-hydroxyl ends of RNA in the presence of ATP, has been isolated from extracts of HeLa cell nuclei.  The kinase requires a divalent cation (Mg2+ or Mn2+) for activity, has an alkaline pH optimum, and is sensitive to the sulfhydryl antagonist N-ethylmaleimide.  5'-hydroxyl terminated polydeoxyribonucleotides are phosphorylated much less efficiently than the 5'-hydroxyl terminated polyribonucleotides, and the kinase preparation is inactive on ribonucleoside 3'-monophosphates.  Enzyme activity is inhibited by ADP and by pyrophosphate.  The sedimentation coefficient of the kinase is estimated to be 5.6 S from glycerol gradient centrifugation.