Table 2.
GTPase Activity and Assembly Dynamics of Fluorophore-Labeled FtsZ in Seven Different Buffersa
| lifetime of disassembly, τ (s) |
|||||
|---|---|---|---|---|---|
| GTPase activity (GTP min−1 FtsZ−1) | 1/GTPase (s)b | lifetime of subunit exchange, τ (s) | GDPc | dilutionc | |
| HMK100 | 4.5 | 13.3 | 5.0 ± 0.5 | 3.6 ± 0.4 | 2.0 ± 0.3 |
| HMK350 | 1.3 | 46.2 | 25.1 ±3 [5 and 33(1:4)]d | 18.9 ± 2.1 | 16.3 ± 2.0 |
| HMK500 | 0.6 | 100 | 32.3 ± 3 | 30.9 ± 4.1 | 27.2 ± 2.9 |
| HMRb100 | 1.8 | 33.3 | 14.1 ± 2 | 5.0 ± 0.4 | 3.6 ± 0.4 |
| HMRb500 | 0.6 | 100 | 54.9 ± 5 | 19.4 ± 2.5 | 17.5± 2.2 |
| HMK100/10Mg | 2.1 | 28.6 | 15.8 ± 2 [5 and 23(1:1.3)]d | 8.9 ± 1.5 | 8.0 ± 1.4 |
| HMK100/20Mg | 0.9 | 66.7 | 20.1 ± 2 [5 and 24 (1:5)]d | 20.0 ± 3.5 | 18.6 ± 2.5 |
a
All measurements were taken at 25–26 °C. τ can be converted to half-time by the formula t1/2 = τ ln 2 = 0.69τ.
b
The time of 1/GTPase can be considered the average time for nucleotide hydrolysis by polymerized FtsZ at steady state.
c
FtsZ filament disassembly was induced by addition of GDP to a 20-fold excess or by 15-fold dilution with the same buffer.
d
The data were best fit by a double-exponential decay. The two lifetimes and the ratio of the amplitudes of their contributions to the decay are given in parentheses. The ratio 1:4 means that the slow decay contributed 4 times as much as the fast decay.