Alternative RNA degradation pathways by the exonuclease Pop2p from Saccharomyces cerevisiae

Exonuclease activity of mutant Pop2p variants. (A) Structure of the S. cerevisiae Pop2p exonuclease domain (PDB: 1UOC). Blue spheres represent the Mg²⁺ ions extrapolated from the S.p. Pop2p exonuclease domain (PDB: 2P51). Amino acids in the catalytic center are marked red. (B) Representative PAGE for exonuclease reactions of Pop2p variants (as indicated) (1000 nM) with A₃₆ (1 nM). Aliquots were removed at 1, 5, 10, 20, 30, 40, and 50 min. (C). Observed rate constants (removal of first nucleotide) for degradation of A₃₆ with the Pop2p variants indicated. Error bar represents the standard error from fitting time courses to rate equations.