Table III.
Summary of double step events b
| Myosin | Mean displacement | Displacement duration | Displacement variance | Normalized variance | |
|---|---|---|---|---|---|
| nm | ms | nm2 | |||
| M5HMM | Step 1 | 19 ± 1 | 213 ± 38 | 55 ± 3 | 0.58 ± 0.02 |
| Step 2 | 18 ± 1 | 687 ± 132a | 64 ± 4a | 0.68 ± 0.03a | |
| Unitary steps | 18 ± 1 | 192 ± 17 | 59 ± 1 | 0.61 ± 0.01 | |
| Step 1 | 12 ± 1 | 468 ± 134 | 26 ± 2 | 0.58 ± 0.04 | |
| Step 2 | 9 ± 2 | 400 ± 95 | 17 ± 1a | 0.38 ± 0.01a |
Values are means ± SEM. M5HMM double steps, n = 59 events; unitary steps, n = 357 events. Normalized variance is the ratio of event variance to baseline variance for that experiment.
a
Significant differences between step 1 and 2 of each myosin type was determined by Student's t test (p < 0.01).
b
The myosin II used was a baculovirus-expressed (–)insert isoform of smooth muscle myosin HMM (Lauzon et al., 1998) with experiments done at an ATP concentration of 10 μM (n = 25 events). Displacement amplitude, duration, and variance were calculated from hand-tallied events.