Ability of fluorescent protein-tagged DHPRs to restore EC coupling
| Construct | ΔF/F-V | Contracting cells/number tested | ||
| [ΔF/F]max | VF | kF | ||
| mV | mV | |||
| α1S-YFPa | 0.58 ± 0.09 (15) | 6.6 ± 1.6 | 4.7 ± 0.4 | 41/47 |
| α1S(671-CFP-YFP) + (686)α1S | 0.61 ± 0.08 (9) | 0.4 ± 1.5 | 3.7 ± 0.4 | 9/11b |
| α1S(671) + (CFP-YFP-686)α1S | 0.48 ± 0.07 (6) | 7.1 ± 2.0 | 3.7 ± 0.4 | 12/15 |
| α1S(671-CFP) + (YFP-686)α1S | 0.93 ± 0.14 (7) | 7.8 ± 1.5 | 4.1 ± 0.4 | 10/25 |
| α1S(671-CFP-YFP-686) | 0.69 ± 0.12 (7) | −0.3 ± 2.7 | 4.9 ± 1.1 | 26/32 |
| α1S(726-CFP-YFP-727) | No fit (12) | No fit | No fit | 0/52 |
| α1S(726-YFP-727) | 0.19 ± 0.08 (7)c | 11.9 ± 3.2d | 10.0 ± 2.8d | 5/56 |
| α1S(726-YFP-727) (10 mM Mg2+ external) | 0.29 ± 0.17 (4) | 4.4 ± 6.0 | 9.1 ± 2.0 | ND |
| α1S(760-YFP-761) | See legend (6) | See legend | See legend | 0/72 |
| α1S(785-YFP-786) | No fit (3) | No fit | No fit | 0/29 |
| Uninjected dysgenic myotubes | No fit (8) | No fit | No fit | 0/100 |
| Construct | ΔF/F-V | Contracting cells/number tested | ||
| [ΔF/F]max | VF | kF | ||
| mV | mV | |||
| α1S-YFPa | 0.58 ± 0.09 (15) | 6.6 ± 1.6 | 4.7 ± 0.4 | 41/47 |
| α1S(671-CFP-YFP) + (686)α1S | 0.61 ± 0.08 (9) | 0.4 ± 1.5 | 3.7 ± 0.4 | 9/11b |
| α1S(671) + (CFP-YFP-686)α1S | 0.48 ± 0.07 (6) | 7.1 ± 2.0 | 3.7 ± 0.4 | 12/15 |
| α1S(671-CFP) + (YFP-686)α1S | 0.93 ± 0.14 (7) | 7.8 ± 1.5 | 4.1 ± 0.4 | 10/25 |
| α1S(671-CFP-YFP-686) | 0.69 ± 0.12 (7) | −0.3 ± 2.7 | 4.9 ± 1.1 | 26/32 |
| α1S(726-CFP-YFP-727) | No fit (12) | No fit | No fit | 0/52 |
| α1S(726-YFP-727) | 0.19 ± 0.08 (7)c | 11.9 ± 3.2d | 10.0 ± 2.8d | 5/56 |
| α1S(726-YFP-727) (10 mM Mg2+ external) | 0.29 ± 0.17 (4) | 4.4 ± 6.0 | 9.1 ± 2.0 | ND |
| α1S(760-YFP-761) | See legend (6) | See legend | See legend | 0/72 |
| α1S(785-YFP-786) | No fit (3) | No fit | No fit | 0/29 |
| Uninjected dysgenic myotubes | No fit (8) | No fit | No fit | 0/100 |
Data are given as mean ± SEM, with the numbers in parentheses indicating the number of myotubes tested. All ΔF/F-V data given were fit with Eq. 2 except for α1S(760-YFP-761). The ΔF/F-V relationship for α1S(760-YFP-761) was best fit by the Gaussian function ΔF/F = [ΔF/F]max × exp{−0.5(V − Vo/b)2}, where [ΔF/F]max = 0.1, Vc = 49.2 mV, and b = 25.7 mV (Eq. 3). “No fit” indicates that the ΔF/F-V relationship could not be well fit by either Eq. 2 or Eq. 3 for the number of myotubes indicated. Significant differences between α1S(671-CFP-YFP-686) and the other individual one-piece constructs that were fit by Eq. 2 (i.e., α1S(726-YFP-727)) are indicated.
α1S-YFP data from Bannister and Beam (2005) are included for comparison.
α1S(671-CFP-YFP) + (686)α1S contraction data were obtained from Papadopoulos et al. (2004).
P < 0.005 by t test.
P < 0.05 by t test.