TABLE 4.
Comparison of velocity and detachment rates at low and high free Mg
| Myosin isoform | Velocity (nm/s)a |
1/ton (s−1)b |
ADP release (s−1)c |
|||
|---|---|---|---|---|---|---|
| Low | High | Low | High | Low | High | |
| MV | 368 ± 9 | 153 ± 8 | 14.8 ± 0.4 | 6.1 ± 0.3 | 25.3 ± 1.0 | 12.7 ± 1.1 |
| SKII | 5050 ± 127 | 1984 ± 74 | 1010 ± 25.3 | 396.9 ± 14.9 | ND | ND |
| NMIIA | 231 ± 2 | 91 ± 3 | 46.2 ± 0.5 | 18.2 ± 0.6 | 12.1 ± 0.3 | 6.8 ± 0.1 |
| CMIIB | 645 ± 89 | 420 ± 103 | 108 ± 15 | 70 ± 17 | 226 ± 2.9 | 149 ± 1.7 |
| SMII | 503 ± 14 | 154 ± 5 | 100.6 ± 2.8 | 30.9 ± 1.1 | 123 ± 2.0 | 54.3 ± 0.3 |
a Sliding velocities were determined in the in vitro motility assay in the presence of low free Mg (0.3 mm for all except CMIIB, which is shown at 1.1 mm free Mg for comparison with ADP release) and high free Mg (9 mm).
b Data were determined by (1/ton) = V/duni, where duni was taken from the literature values referenced in the text.
c Data were determined from the mant-dADP release studies in MV (fast phase), NMIIA (fast phase), SMII (free Mg is the same as velocity and 1/ton), and pyrene-actin experiments in CMIIB (low free Mg = 1.5 mm and high free Mg = 9.5 mm).