| . | Apo . | Ca(II) . | Rigor . | Ca(II) . | Actin . |
|---|---|---|---|---|---|
| . | . | . | . | + rigor . | . |
| Skeletal | |||||
| kfast (Pi) | 0.64 s−1 | 16 s−1 | 30 s−1 | 77 s−1 | 75 s−1 |
| Keq TF, fast | 26 μM | 17 μM | 12 μM | 18 μM | |
| kfast md-ADP-Pi | 0.68 s−1 | 18 s−1 | 30 s−1 | 96 s−1 | 125 s−1 |
| Keq TF, fast | 53 μM | 26 μM | 13 μM | 18 μM | 68 μM |
| Cardiac | |||||
| kfast (md-ADP-Pi) | 0.49 s−1 | 27 s−1 | 24 s−1 | 36 s−1 | 38 s−1 |
| Keq TF, fast | 16 μM | 19 μM | 11 μM | 11 μM | 53 μM |
| kfast (md-ADP) | 64 s−1 | 357 s−1 | 332 s−1 | 359 s−1 | 361 s−1 |
| Keq TF, fast | 32 μM | 12 μM | 27 μM | 6 μM | 49 μM |
| . | Apo . | Ca(II) . | Rigor . | Ca(II) . | Actin . |
|---|---|---|---|---|---|
| . | . | . | . | + rigor . | . |
| Skeletal | |||||
| kfast (Pi) | 0.64 s−1 | 16 s−1 | 30 s−1 | 77 s−1 | 75 s−1 |
| Keq TF, fast | 26 μM | 17 μM | 12 μM | 18 μM | |
| kfast md-ADP-Pi | 0.68 s−1 | 18 s−1 | 30 s−1 | 96 s−1 | 125 s−1 |
| Keq TF, fast | 53 μM | 26 μM | 13 μM | 18 μM | 68 μM |
| Cardiac | |||||
| kfast (md-ADP-Pi) | 0.49 s−1 | 27 s−1 | 24 s−1 | 36 s−1 | 38 s−1 |
| Keq TF, fast | 16 μM | 19 μM | 11 μM | 11 μM | 53 μM |
| kfast (md-ADP) | 64 s−1 | 357 s−1 | 332 s−1 | 359 s−1 | 361 s−1 |
| Keq TF, fast | 32 μM | 12 μM | 27 μM | 6 μM | 49 μM |
The columns are for thin filaments (low ionic strength, 20°C, pH 7) with no bound ligands (apo); Ca(II) alone, rigor myosin-S1 alone and Ca(II) plus rigor myosin-S1. Actin, unregulated actin. Skeletal, skeletal thin filaments and skeletal myosin-S1A1. Cardiac, native cardiac thin filaments and cardiac myosin-S1. The data are of the fast component of the fluorescence change, which is due to the conversion of AM-NDP-Pi to AM-NDP + Pi. The slower component is not included. kfast (Pi), the maximum rate for the dissociation of Pi (as obtained with fluorescent PBP) from regulated actomyosin-S1-ADP-Pi; kfast (md-ADP-Pi), the maximum rate for dissociation of md-ADP from regulated actomyosin-S1-md-ADP-Pi; kfast (md-ADP), the maximum rate for dissociation of md-ADP from regulated actomyosin-S1-md-ADP. Keq TF, fast, thin filament (actin subunit) concentration at half-maximal rate.