Two Distinct Poly(A) Polymerases Isolated from the Cytoplasm of Ehrlich Ascites Tumour Cells

Zoya V. AVRAMOVA, Georgui I. MILCHEV, Asen A. HADJIOLOV

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

The poly(A) polymerases from the cytosol and ribosomal fractions of Ehrlich ascites tumour cells are isolated and partially purified by DEAE‐cellulose and phosphocellulose column chromatography. Two distinct enzymes are identified: (a) a cytosol Mn2+‐dependent poly(A) polymerase (ATP: RNA adenylyltransferase) and (b) a ribosome‐associated enzyme defined tentatively as ATP(UTP) :RNA nucleotidyltransferase. The cytosol poly(A) polymerase is strictly Mn2+‐dependent (optimum at 1 mM Mn2+) and uses only ATP as substrate, Poly(A) is a better primer than ribosomal RNA. The purified enzyme is free of poly(A) hydrolase activity, but degradation of [3H]poly(A) takes place in the presence of inorganic pyrophosphate. Most likely this enzyme is of nuclear origin. The ribosomal enzyme is associated with the ribosomes but it is found also in free state in the cytosol. The purified enzyme uses both ATP and UTP as substrates. The substrate specificity varies depending on ionic conditions: the optimal enzyme activity with ATP as substrate is at 1 mM Mn2+, while that with UTP as substrate is at 10–20 mM Mg2+. The enzyme uses both ribosomal RNA and poly(A) [but not poly(U)] as primers. The purified enzyme is free of poly(A) hydrolase activity.

Original languageEnglish (US)
Pages (from-to)99-107
Number of pages9
JournalEuropean Journal of Biochemistry
Volume103
Issue number1
DOIs
StatePublished - Jan 1980

ASJC Scopus subject areas

  • Biochemistry

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