Table 4.
Effect of tropomyosin on the biochemical properties of Myo2p
| Property | No Cdc8p | +Cdc8p |
|---|---|---|
| In vitro motility (μm · s−1)a | ||
| Myo2p | 0.69 ± 0.04 | 0.35 ± 0.02 |
| Control: myosin-Va HMM | 0.22 ± 0.03 | 0.23 ± 0.02 |
| Actin-activated Mg2+-ATPaseb | ||
| Km (μM) | 20.4 ± 2.9 | 3.0 ± 0.8 |
| VMAX (s−1)c | 3.5 ± 0.2 | 4.9 ± 0.2 |
| ton (ms)d | 14.5 | 28.6 |
| Duty ratio (%)e | ||
| i) | 5.1 | 14.0 |
| ii) | 3.2 ± 0.3 | 5.8 ± 0.4 |
a n = 50 filaments. Rates (±SD) derived using 32 μg/ml myosin (plus excess calmodulin for myosin-Va HMM).
b Values are derived from curves in Figure 6A (±SE).
c ATPase activity: molecules of ATP hydrolyzed per motor per second.
d Values calculated using the equation: v = d/ton, where v = motility rate, and d = step size (assumed to be 10 nm).
e Values represent i) the percentage of time ton is occupied within an ATPase cycle time (derived from VMAX values) and ii) experimental values derived from curves in Figure 8D (±SE).