Table 1.
Actin-activated ATPase activity (Vmax) and rotary shadowing electron microscopy of myosin VI constructs
| Construct (protocol) | Vmax | Dimers, % |
|---|---|---|
| FL-Myosin VI | 4.6 ± 0.1 | 0 |
| FL-Myosin VI + optineurin (Protocol I) | 4.6 ± 0.1 | N.D. |
| FL-Myosin VI + optineurin (Protocol II) | 2.6 ± 0.3 | 16.9 ± 8 |
| FL-Myosin VI + tDab2 | 3.3 ± 0.4 | 1.8 ± 0.3 |
| FL-Myosin VI + 5 μM tDab2 | 2.8 ± 0.4 | N.D. |
| Myosin VI-1050 | 4.7 ± 0.3 | 0 |
| Myosin VI-1050 + tDab2 | 4.4 ± 0.4 | N.D. |
| Myosin VI zippered dimer | 2.4 ± 0.8 | 100 |
Actin-activated ATPase: mean values (±SD) of ATP hydrolyzed head−1sec−1 for three or four independent protein preparations are shown for each construct and condition. Protocol I results in one myosin VI monomer bound to an optineurin dimer, whereas Protocol II results in two myosin VI molecules bound to an optineurin dimer. Rotary shadowing EM (mean ± SD): Data were obtained from a single spray experiment, 2–10 electron micrographs, and a total of 40–100 molecules. The following populations are significantly different (Student's t test with confidence at 95%): FL-MVI/FL-MVI + optineurin (P < 0.003); FL-MVI/FL-MVI + tDab2 (P < 0.001). FL-MVI is the full-length construct (amino acids 1–1,273).