Table 2.
Relative affinities for association of PfHsp70-1 with its interactors in the presence of nucleotide and/or PMB
| Analyte, ligand | Nucleotide | K D (M) | χ 2 | Reference |
|---|---|---|---|---|
| PfHsp70-1, PfHsp70-z | ATP | 2.41 (± 0.2) e−08 | 1.86 | Zininga et al. 2016 |
| ADP | 1.21 (± 0.1) e−06 | 2.12 | Zininga et al. 2016 | |
| NN | 5.98 (± 0.5) e−05 | 3.32 | Zininga et al. 2016 | |
| PMB | 2.50 (± 0.8) e−04* | 2.65 | This study | |
| PfHsp70-1NBD, PfHsp70-z | ATP | 2.12 (± 0.2) e−09 | 2.65 | Zininga et al. 2016 |
| ADP | 9.86 (± 0.9) e−08 | 6.52 | Zininga et al. 2016 | |
| NN | 1.57 (± 0.6) e−08 | 2.44 | Zininga et al. 2016 | |
| PMB | 8.41 (± 0.7) e−05** | 4.72 | This study | |
| PfHsp70-1, PfHop | ATP | 1.13 (± 0.5) e−08 | 2.15 | Zininga et al. 2015b |
| ADP | 1.72 (± 0.5) e−09 | 2.30 | Zininga et al. 2015b | |
| NN | 1.91 (± 0.01) e−09 | 2.17 | Zininga et al. 2015b | |
| PMB | 1.60 (± 0.08) e−06** | 1.22 | This study |
The interaction kinetics represented by the equilibrium constant (K D) were determined by SPR analysis alternating the status of PfHsp70-z/PfHop and PfHsp70-1/PfHsp70-1NBD as ligand and analyte, respectively. The ligand was the respective immobilized protein on the GLC chip surface and the analyte was the respective protein injected at a flow rate of 50 μl/min. Data were analyzed by using readings obtained for the running buffer (in the presence of nucleotides, but in the absence of protein analyte) as baseline (Fig. 4). Data are represented as mean plus/minus standard deviation. Chi-square (χ 2) values represent the Langmuir curve fitting residuals. Statistical analysis was conducted using one-way ANOVA. *p < 0.005, **p < 0.001 represents statistically significant differences in affinities noted under the variable experimental conditions