TABLE 3.
Ca2+ transients expressed by domain chimeras and heptad repeat mutants in β1 KO myotubes
| 50 ms F-V
|
200 ms F-V
|
|||||
|---|---|---|---|---|---|---|
| ΔF/Fmax | V1/2 (mV) | k (mV) | ΔF/Fmax | V1/2 (mV) | k (mV) | |
| WT β1a | 2.7 ± 0.5 (10) | −3 ± 2 | 7.7 ± 0.5 | 3.4 ± 0.6 (10) | −8 ± 2 | 5.8 ± 1.1 |
| WT β2a | 0.9 ± 0.2* (10) | −2 ± 3 | 7.4 ± 1.5 | 1.7 ± 0.4* (10) | 6 ± 3 | 7.6 ± 1.9 |
| β2a(D1–D3)/β1a(D4, D5) | 2.8 ± 0.6 (8) | −2 ± 3 | 7.8 ± 1.1 | 2.9 ± 0.4 (9) | −7 ± 3 | 5.9 ± 1.2 |
| β1a(D1–D3)/β2a(D4, D5) | 0.2 ± 0.1* (7) | 24 ± 11* | 23.0 ± 4.1* | 0.7 ± 0.1* (6) | 14 ± 2* | 6.5 ± 2.1 |
| β2a(D1–D4)/β1aD5 | 2.4 ± 0.5 (8) | 4 ± 3 | 8.2 ± 1.8 | 2.6 ± 0.6 (9) | −4 ± 2 | 4.8 ± 1.3 |
| β1a(D1–D4)/β2aD5 | − (5) | − | − | − (5) | − | − |
| β2a(D1–D4)/β2aD5/β1aD5 | 0.3 ± 0.1* (11) | 6 ± 4 | 15.2 ± 3.2 | 1.0 ± 0.3* (11) | 12 ± 3* | 7.6 ± 1.2 |
| β2a(D1–D4)/β1aD5/β2aD5 | 2.2 ± 0.4 (5) | 18 ± 5 | 9.6 ± 2.1 | 2.5 ± 0.8 (5) | 8 ± 6 | 7.2 ± 2.7 |
| β1a(D1–D4)/β1aD5/β2aD5 | 1.9 ± 0.5 (9) | 12 ± 3 | 12.0 ± 1.7 | 2.2 ± 0.2 (7) | 11 ± 4 | 10.2 ± 1.6 |
| β1a(D1–D4)/β2aD5/β1aD5 | 0.4 ± 0.1 (3/7) | 17 ± 11 | 19.2 ± 1.7 | 0.5 ± 0.1* (5) | 11 ± 4 | 9.4 ± 2.1 |
| D5ALA (L478A, V485A, V492A) | 0.4 ± 0.1* (8) | 12 ± 3 | 20.0 ± 4.3 | 0.7 ± 0.2* (8) | 15 ± 5 | 11.4 ± 2.2 |
| D5ALAc (S481A, L488A, S495A) | 2.1 ± 0.4 (7) | 14 ± 2 | 7.2 ± 1.7 | 2.6 ± 0.5 (7) | 16 ± 5* | 9.1 ± 3.4 |
Mean ± SEM of Boltzmann parameters fitted to each cell with number of cells in parentheses. Parameters of fluorescence versus voltage curves are shown for 50 ms and 200 ms depolarizations. ΔF/Fmax, V1/2, and k are parameters of the Boltzmann fit to each cell. All data was fit with Eq. 1 except fluorescence data in response to 200 ms in cells expressing β1a(D1–D3)/β2a(D4, D5), β2a(D1–D4)/β2aD5/β1aD5, and β1a(D1–D4)/β2aD5/β1aD5, which were fit with Eq. 2.
*
Parameters in each column compared to WT β1a with one-way ANOVA significance p < 0.05. Data for WT β1a and WT β2a are from Sheridan et al. (2003b).