TABLE 1.
Apparent dissociation constants of hHP1β as determined by different experimental methods
The following abbreviations are used: FP, fluorescence polarization; ITC, isothermal titration calorimetry; and SPR, surface plasmon resonance. Kd values represent averages and standard deviation of multiple independent measurements (FP), including different concentrations of hHP1β and peptides or nucleosomes (ITC) or varying immobilization levels of peptides or nucleosomes (SPR).
| Kd (μm), hHP1β | Kd (μm), CSD | |
|---|---|---|
| H3K9me3 nucleosome | 2.4 ± 1.9 at SPR | |
| H3KC9me3 nucleosome | 8.0 ± 0.3 at SPR | NBa at ITC |
| 22 ± 17 at ITC | ||
| Unmodified nucleosome | NDb at SPR | |
| K9me3 H3(1–15) peptide | 1.9 ± 0.6 at FP | NBa at FP |
| 0.9 ± 0.3 at SPR | ||
| 1.4 ± 0.6 at ITC | ||
| KC9me3 H3(1–15) peptide | 7.5 ± 2.6 at FP | |
| 11 ± 4 at ITC | ||
| Unmodified H3(1–15) peptide | >300c at FP | NBa at FP |
| >300c at SPR | ||
| >500c at ITC |
a NB means not binding; titration curves could not be analyzed due to lack of binding signals.
b ND means not determined; although interaction was clearly observed, no binding constants could be deduced faithfully due to the limited number of data points (see supplemental Fig. 1N for details).
c In the case where titration curves did not reach the inflection points, minimal values for Kd are given.