FlaI, or FlaI in the presence of ADP or p[NH]ppA were analysed on an analytical size-exclusion column (Superdex 200). The elution fractions were analysed on SDS/PAGE and stained with Coomassie Blue. Arrows indicate the position of the marker proteins used to calibrate the column. Prior to analytical gel filtration, the purified FlaI (1 μM) was pre-incubated at 50°C for 10 min followed by an incubation at 4°C for 6 h with either 1 mM p[NH]ppA or ADP, and 10 mM MgCl2. The molecular mass standards used were: ribonuclease A, 13.7 kDa; carboxy anhydrase, 29 kDa; ovalbumin, 43 kDa; conalbumin, 75 kDa; aldolase, 158 kDa; and ferritin, 440 kDa. AMPPNP, p[NH]ppA.