Table 5. Proteins of the ER/SR lumen.
Resident luminal ER/SR proteins, listed in order of decreasing ASR. Proteins known to be highly specific for cardiac and skeletal muscle myocytes cells are indicated (shaded rows) [18]. All other proteins likely act as ER protein chaperones, and are maintained in ER through a C-terminal –KDEL retrieval signal (asterisk*). Calnexin is a Type I transmembrane protein with a large luminal segment that has calreticulin-like chaperone activity [59]. GRP78, glucoseregulated protein, Mr = 78 kDa; PDI, protein disulfide isomerase; His-rich Ca BP, histidine-rich Ca binding protein. Rank identifies proteins by their order among 354 proteins in SERCA-positive SR sorted by ASR (see Online Resource 1).
| Protein | KDEL | Rank | ASR | ESR | Esub |
|---|---|---|---|---|---|
| sarcalumenin | 3 | 73.2 | 4.6 | 0.42 | |
| calsequestrin | 5 | 41.1 | 4.7 | −0.15 | |
| GRP78 | * | 13 | 17.3 | 5.0 | 0.49 |
| PDI A3 | * | 32 | 9.6 | 6.2 | 0.36 |
| GRP94 | * | 36 | 8.5 | 5.7 | 0.54 |
| calnexin | 41 | 7.7 | 6.8 | 0.36 | |
| PDI A2 | * | 73 | 4.9 | 5.1 | 0.46 |
| PDI A4 | * | 91 | 4.3 | 7.8 | 0.40 |
| PDI A6 | * | 94 | 4.2 | 15.2 | 0.59 |
| calreticulin | * | 142 | 2.4 | 8.5 | 0.54 |
| PDI | * | 145 | 2.3 | 7.0 | 0.41 |
| PDI isoform TMX | * | 159 | 2.1 | 6.8 | 0.11 |
| His-rich Ca BP | 217 | 1.2 | 5.0 | 0.19 |