Table 2.
Effect of Ca2+ binding in EF hand 2 on activation of RetGC-1 by EF(3,4)− mutant
| Mutantsa | Amaxb nmol cGMP/mg/min | K1/2c µM |
|---|---|---|
| GCAP-1 EF(3,4)− in EGTA | 16 ± 3.6 (N=4) | 4.4 ± 0.8 (N=4) |
| GCAP-1 EF(3,4)− at 10 µM [Ca]f | 22 ± 3.5 (N=3) | 1.2 ± 0.3 (N=3) |
| GCAP-1 E75Q/EF(3,4)− in EGTA | 18 ± 1.0 (N=3) | 6.3 ± 0.3 (N=3) |
| GCAP-1 E75Q/EF(3,4)− at 10 µM [Ca]f | 15 ± 1.0 (N=3) | 4.2 ± 0.3 (N=3) |
a
GCAP-1 EF(3,4)− and GCAP-1 E75Q/EF(3,4)− represent GCAP-1(D100N/D102G/D144N/D148G) and GCAP-1(E75Q/D100N/D102G/D144N/D148G), respectively.
b
Amax, the maximal level of RetGC-1 activation by GCAP at indicated free Ca2+ in the presence of 5 mM free Mg2+ (mean ± S.D., N is the number of independent measurements)
c
K1/2, the concentration of GCAP required for half-maximal activation of RetGC-1 (mean ± S.D., N is the number of independent measurements)