Table 1. Summary of enzymatic and mechanical properties of myosin.
| Myosin | Vmax,* s-1 | Km,* μM | Vactin,† μm/s | d, nm | τon, ms |
|---|---|---|---|---|---|
| Native | 5.3 | 1.6 | 10.6 ± 1.7 (48) | 9.7 ± 2.4 (9) | 34.5 ± 8.1 (9) |
| Exchanged | |||||
| F102 | — | — | 7.1 ± 1.3 (82) | 8.1 ± 2.4 (12) | 30.1 ± 13.1 (15) |
| F102L | — | — | 5.1 ± 1.1** (83) | 6.1 ± 2.8** (27) | 29.5 ± 14.2 (27) |
| Reconstituted | |||||
| F102 | 5.4 | 1.4 | 8.4 ± 1.8 (77) | 9.6 ± 2.7 (19) | 25.9 ± 13.1 (11) |
| F102L | 5.6 | 1.2 | 4.6 ± 1.0** (82) | 3.8 ± 2.4** (8) | 31.6 ± 12.1 (8) |
| Single-headed | |||||
| F102 | 4.5 | 13.4 | 8.6 ± 1.5 (108) | — | — |
| F102L | 4.3 | 14.2 | 4.1 ± 0.8** (136) | — | — |
Data are presented as mean ± SD. Data in parentheses are the number of actin filaments measured for Vactin or the number of MV histograms contributing to the mean d and τon. Optical trap data were collected at 10 μM MgATP with 2- to 5-fold molar excess light chains. Except for the single-headed myosin, the in vitro motility assays were performed on the same preparations used for the unitary mechanical measurements.
Statistically significant vs. WT at the P < 0.001 level by Student's t test.
The ATPase parameters (Vmax and Km) are representative activity data for the different myosin preparations.
In addition to the actin filament velocities shown here, earlier data for exchanged and reconstituted double-headed myosin gave essentially the same results.