Fig. 6.

ATPase inhibition assay by Walker B mutants reveals complete negative cooperativity. The inhibition ability of the Walker B mutants E119A and D118E/E119D was assayed by ATPase activity in the absence (left) and presence (right) of dsDNA. In the presence of DNA (right), the experimental data (solid line) overlapped with a theoretical curve indicating that one inactive subunit (dotted line) within the hexamer is able to completely block the activity of the hexameric gp16 and abolish ATPase activity, demonstrating negative cooperativity (see also Fig. 4). The dashed line is the theoretical curve where two inactive subunits are necessary for inhibition.