Table 5. Relative association constants from EMSA of MelR303 with different DNA fragments.
| DNA fragment | K1 (106 M) | K2 (1012 M2) | kA (106 M) | kB (106 M) | kAB |
|---|---|---|---|---|---|
| KK98 | 1.3 ± 0.2 | 2.8 ± 0.6 | 1.25 | n.d. | n.d. |
| KK99 | 1.2 ± 0.3 | 19 ± 2.2 | 1.25 | n.d. | n.d. |
| KK100 | 2.5 ± 0.3 | 46 ± 9 | 1.25 | 1.25 | 31 |
The K1 and K2 values are the macroscopic association constants from several gels with the data fitted simultaneously in Sigmaplot. From these K1 and K2 values, the microscopic association constants for binding to individual sites, kA and kB, and the cooperativity constant, kAB, have been estimated for the KK100 DNA fragment with two equivalent sites, assuming that kA and kB are identical. For the KK98 and KK99 fragments, kA is assumed to be the same as for KK100 with MelR303. The errors shown are those from the fit, which are similar to those obtained from fitting data from each gel individually for a given protein preparation. When different protein preparations were used the relative affinities of the pairs of fragments remained the same, as did the ratios of K1/K2, but the absolute values differed, presumably due to different specific activities of the preparations. The values of the association constants for this preparation are much lower than for the one used in Figures 4 and 5. n.d., not determined.