Table 4. Summary of MS data from α-cardiac myosin extracted from mouse hearts.
| Tg WT RLC | Tg K104E RLC | |
|---|---|---|
| Protein (%) | ||
| Mouse WT RLC | 4.3 ± 1.8 | 46.6±5.1 |
| Human WT RLC | 95.7 ± 1.8 | — |
| Human K104E RLC | — | 53.4 ± 5.1 |
| α-Cardiac myosin (Myh6) | 98.3 ± 0.5 | 97.1 ± 1.7 |
| Peptidea | ||
| IEGGSpSNVFSMFEQTQIQEFK (mRLC, singly phosphorylated) | 10.0 ± 5.6 | 5.1 ± 0.3 |
| IEGGSpSpNVFSMFEQTQIQEFK (mRLC, doubly phosphorylated) | 0.6 ± 0.3 | 0.3 ± 0.1 |
| AGGANSpNVFSMFEQTQIQEFK (hRLC, phosphorylated) | 11.9 ± 10.4 | 3.4 ± 1.2 |
All data are averages ± SD where n = 3. hRLC, human RLC; mRLC, murine RLC.
a
Data are expressed as the ratio of the phosphopeptide and the nonphosphopeptide. These ratios do not account for the difference in the ionization efficiencies between the peptides and should not be interpreted as absolute phosphorylation levels.