Figure 4.

SyFtsZ assembly in buffers of different pH. A, assembly kinetics of 5 μm SyFtsZ monitored by light scattering. The light-scattering signals were much higher when the pH dropped from 7.5 to 6.5. B–E, negative-stain EM images of 10 μm SyFtsZ assembled at different pH levels, from 7.5 to 6.5. Bar, 1 μm. F, GTPase activity of SyFtsZ was measured after the assembly reached a plateau. GTPase is approximately the same at pH 6.5–7.5. All buffers contained 100 mm KAc, 5 mm MgAc, and 0.5 mm GTP. pH 7.5 and 7.2 were buffered with HEPES; pH 6.8 and 6.5 were buffered with MES. Error bars, S.D.