TABLE 2.
IP3 binding to the NT and IBC determined by saturation and competition binding assays
To increase the sensitivity of the assay, the direct comparison of [3H]IP3 saturation and competition binding assays was determined in TEM (Fig. 2, D and E). For comparison, results are shown for competition binding assays in CLM (Fig. 3 and Supplemental Fig. 5); these were used to determine the concentration of IP3-binding sites in each preparation of NT and IBC. The KD, Bmax, and Hill coefficient values are shown for each assay. Results are means ± S.E.M., n = 3.
| TEM |
CLM |
|||
|---|---|---|---|---|
| Saturation NT | Competition NT | Competition NT | Competition IBC | |
| KD (nM) | 2.2 ± 0.5 | 1.7 ± 0.2 | 65.2 ± 8.2 | 8.7 ± 1.8 |
| Bmax (nmol/mg) | 1.5 ± 0.1 | 1.2 ± 0.1 | 1.3 ± 0.1 | 0.44 ± 0.03 |
| Hill coefficient | 0.8 ± 0.1 | 1.1 ± 0.1 | 0.9 ± 0.1 | 0.9 ± 0.1 |