FIGURE 2.

Dephosphorylation of m⁷GMP is catalyzed by a specific nucleotidase. A, Schneider 2 cells were disrupted as described under “Experimental Procedures,” and cytosolic proteins were fractionated on a DEAE-Sepharose column. Nucleotidase activity of the fractions was determined by an assay with 40 μm m⁷GMP trace-labeled with [³²P]m⁷GMP. B, an aliquot of fraction 16 of the DEAE column in A was incubated with either GMP or m⁷GMP (400 μm) for 25 min at 25 °C. The reaction was stopped by the addition of EDTA, and HPLC analysis was carried out as described under “Experimental Procedures.” mAU, milliabsorbance units.