Light scattering and GTPase activity of TubZ-Ba measured in the presence
of non-hydrolyzable GTP analogues, GTPγS or GMPCPP. a,
assembly measured by light scattering of 5 μm TubZ-Ba in 100
μm GTP; in 1.5 μm GTPγS, with 100
μm GTP added at 400 s; and in 1.5 μm GTPγS
plus 100 μm GTP added together at time 0. b, inhibition
of GTPase activity of TubZ-Ba by GTPγS. Data are shown for 5
μm TubZ-Ba and increasing GTPγS, plus 20, 100, and 500
μm GTP. c, inhibition of GTPase activity by GMPCPP.
d, plot of 1/GTPase activity versus GMPCPP concentration,
showing that the relationship is not linear. The curvature indicates that the
inhibition is cooperative. e, plot of 1/GTPase activity
versus GMPCPP concentration for 5 μm FtsZ and 100
μm GTP. In contrast to TubZ, this plot is linear. f,
Hill plot of the GTPase inhibition by GTPγS and GMPCPP. The five lines
on the left are for TubZ-Ba, with Hill coefficients of 1.7–1.9,
and the line on the right is for FtsZ, with a Hill coefficient of
1.