Size distribution of cytosolic TK1. TK1 activity in each fraction was measured using [3 H]-dThd as substrate. MDCK extracts (A) and CEM extracts (B) analyzed directly (○) or treated with DTE (●) prior to chromatography. Arrows indicate the elution position of the molecular weight markers. Western blot analyses of cytosolic canine TK1 (C) and human TK1 (D) in the FPLC fractions using polyclonal anti-dog TK1 antibody or mouse monoclonal anti-TK1 antibody for detection. Pre-treatment with DTE is indicated as + DTE. The numbers represent FPLC fractions.