TABLE 2.
Affinity for ATP of SR and expressed wild type Ca2+-ATPase and mutants in various stabilized states
KD values derived from competitive inhibition of photolabeling by ATP (Figs. 2, 5, and 7) are indicated relative (in %) to that of the expressed wild type obtained under the same conditions (for wild type the absolute KD value is shown). The S.E. is indicated with the number of experiments in parentheses.
| EDTAa |
EGTA/Mg2+b | |||||
|---|---|---|---|---|---|---|
| E2 (Tg) | E2·Pi (MgF) | E2·P (vanadate) | E2·P (AlF) | E2−P (BeF) | E1 | |
| Wild type | 100 ± 9 (n = 8) (10.8 μm) | 100 ± 19 (n = 5) (0.89 μm) | 100 ± 9 (n = 4) (1.01 μm) | 100 ± 7 (n = 7) (1.33 μm) | 100 ± 7 (n = 6) (4.1 μm) | 100 ± 5 (n = 4) (0.14 μm) |
| SR | 96 ± 8 (n = 5) | 90 ± 7 (n = 3) | 81 ± 6 (n = 3) | 52 ± 6 (n = 4) | 60 ± 6 (n = 3) | 78 |
| R174A | 316 ± 38 (n = 2) | 256 ± 29 (n = 2) | 224 ± 42 (n = 2) | 256 ± 8 (n = 2) | 1070 ± 61 (n = 2) | 182 |
| R174E | 503 ± 4 (n = 2) | 3445 ± 168 (n = 2) | 2579 ± 272 (n = 2) | 1157 ± 15 (n = 2) | 4307 ± 964 (n = 3) | 425 |
| I188A | 75 ± 1 (n = 2) | 43 ± 4 (n = 2) | 47 ± 4 (n = 2) | 56 ± 6 (n = 2) | 31 ± 4 (n = 2) | 45 |
| I188F | 97 ± 17 (n = 3) | 187 ± 12 (n = 2) | 91 ± 2 (n = 2) | 56 ± 0 (n = 2) | 476 ± 68 (n = 2) | 110 |
| K205A | 267 ± 2 (n = 2) | 1147 ± 117 (n = 2) | 1257 ± 10 (n = 2) | 1198 ± 26 (n = 2) | 249 ± 36 (n = 3) | 139 |
| E439A | 78 ± 1 (n = 2) | 195 ± 31 (n = 2) | 237 ± 8 (n = 2) | 631 ± 74 (n = 3) | 32 ± 5 (n = 3) | 235 |
| F487L | 1594 ± 121 (n = 2) | 133 ± 10 (n = 2) | 138 ± 0 (n = 2) | 127 ± 17 (n = 2) | 354 ± 10 (n = 2) | 2,200 |
| F487S | 1219 ± 14 (n = 2) | 1717 ± 450 (n = 4) | 1294 ± 303 (n = 3) | 1104 ± 53 (n = 2) | 2309 ± 229 (n = 3) | >100,000 |
| R489L | 1896 ± 97 (n = 2) | 252 ± 48 (n = 2) | 285 ± 38 (n = 2) | 203 ± 8 (n = 2) | 1168 ± 283 (n = 2) | 1600 |
| K492L | Not feasible | Not feasible | Not feasible | Not feasible | Not feasible | Not feasible |
| R560L | 3555 ± 23 (n = 2) | 2019 ± 419 (n = 2) | 1977 ± 356 (n = 3) | 1172 ± 150 (n = 2) | 3762 ± 369 (n = 3) | >100,000 |
| L562F | 213 ± 36 (n = 3) | 67 ± 3 (n = 2) | 64 ± 12 (n = 2) | 106 ± 1 (n = 2) | 132 ± 18 (n = 2) | 6,900 |
| 4Gi-46/47 | 261 ± 62 (n = 2) | 89 ± 10 (n = 2) | 75 ± 1 (n = 2) | 102 ± 5 (n = 2) | 93 ± 17 (n = 2) | >100,000 (n = 4) |
a EDTA refers to the condition without free Mg2+ present described under “Experimental Procedures.”