Biophysical and biochemical characterization of recombinant human Pop2 deadenylase

Pop2, a component of the Ccr4-Not complex, functions as a deadenylase both in vitro and in vivo. In this research, we found that the recombinant human Pop2 (hPop2) mainly existed in a compact monomeric state with a a + b tertiary structure type. The percentages of the secondary structures evaluated from the CD spectrum were about 37% a-helix, 14% b-sheet, and 19% b-turns. The optimal condition for hPop2 catalysis was pH 7-8 at 37 C. Mg2+, Mn2+, and Co2+ had similar effects on the deadenylation activity of hPop2, and the optimal concentration was 0.3-0.5 mM. The deadenylase activity of hPop2 was, at least partially, specific when coordinated with divalent metal ions. The enzyme was not inhibited much by the nucleotide analogs, and the product 50-AMP was the most efficient inhibitor. The dissimilarity in the metal ion dependence and inhibitory effects of the nucleotide analogs suggested that various deadenylases might have differential regulation mechanisms.