Table III.

Summary of double step eventsb

MyosinMean displacementDisplacement durationDisplacement varianceNormalized variance
nmmsnm2
M5HMMStep 119 ± 1213 ± 3855 ± 30.58 ± 0.02
Step 218 ± 1687 ± 132a64 ± 4a0.68 ± 0.03a
Unitary steps18 ± 1192 ± 1759 ± 10.61 ± 0.01
Step 112 ± 1468 ± 13426 ± 20.58 ± 0.04
Step 29 ± 2400 ± 9517 ± 1a0.38 ± 0.01a
  • 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.

  • 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.