Poly(A) polymerase from Escherichia coli adenylylates the 3 '-hydroxyl residue of nucleosides, nucleoside 5 '-phosphates and nucleoside(5 ')oligophospho(5 ')nucleosides (NpnN)

The capacity of Escherichia coli poly(A) polymerase to adenylylate the 3'-O H residue of a variety of nucleosides, nucleoside 5'-phosphates and dinucle otides of the type nucleoside(5')oligophospho(5')nucleoside is described he re for the first time. Using micromolar concentrations of [alpha-P-32]ATP, the following nucleosides/nucleotides were found to be substrates of the re action: guanosine, AMP, CMP, GMP, IMP, GDP, CTP, dGTP, GTP, XTP, adenosine( 5')diphospho(5')adenosine (Ap(2)A), adenosine (5')triphospho(5')adenosine ( Ap(3)A), adenosine(5')tetraphospho(5')adenosine (Ap(4)A), adenosine(5')pent aphospho(5')adenosine (Ap(5)A), guanosine(5')diphospho(5') guanosine (Gp(2) G), guanosine(5')triphospho(5')guanosine (Gp(3)G), guanosine(5')tetraphosph o(5')guanosine (Gp(4)G), and guanosine(5')pentaphospho(5')guanosine (Gp(5)G ). The synthesized products were analysed by TLC or HPLC and characterized by their UV spectra, and by treatment with alkaline phosphatase and snake v enom phosphodiesterase. The presence of 1 mm GMP inhibited competitively th e polyadenylylation of tRNA. We hypothesize that the type of methods used t o measure polyadenylation of RNA is the reason why this novel property of E . coli poly(A) polymerase has not been observed previously.