Poly(A) polymerase from <em>Vigna unguiculata</em> seedlings.

Poly(A)-specific ribonuclease was co-purified with poly(A) polymerase from Vigna unguiculata seedlings. Both activities were separated into two forms (enzymes 1 and II) by a final hydrophobic column chromatography. The enzyme I preparation, which was homogeneous as examined by SDS/PAGE, had both poly(A) polymerase and poly(A)-specific ribonuclcase activities. The antibody raised to the enzyme I preparation precipitated both enzyme activities. These indicate that a single polypeptide (M_r 63 000) is responsible for both poly(A)-polymerizing and poly(A)-hydrolyzing activities. The poly(A)-specific ribonuclease was a 3'-exonuclease specific to single-stranded poly(A), forming 5'AMP as the sole reaction product. The hydrolytic activity required either Mn²⁺ or Mg²⁺ with different optimum concentrations, whereas the polymenzing activity required Mn²⁺ but not Mg²⁺ ATP and PP_i had little or no effect on the poly(A)-specific ribonuclease activity. [ABSTRACT FROM AUTHOR]