| Assay Method Information | |
| | TR-FRET Assay |
| Description: | The peptide AVPIAQKSEK-(ε-biotin)-OH 1:2 TFA ("Peptide A") was identified as a substrate for the TR-FRET assay by screening the 6× Histidine-tagged BIR2 domain and BIR3 domain of XIAP against a set of 29 peptides synthesized based on sequences reported by Sweeny et al. (Biochemistry, 2006, 45, 14740 14748). The peptides were labeled with the fluorescent tags FITC or TAMRA and Kd values were determined by fluorescence polarization assay. The sequence AVPIAQKSEK was identified as optimal for using in an assay. The peptide sequence was derivatized with biotin to provide AVPIAQKSEK-(ε-biotin)-OH 1:2 TFA as the substrate for the TR-FRET assay. Ten nanomolar of 6× Histidine-tagged BIR2 domain, corresponding to amino acids 124-240 of XIAP, or BIR3 domain, corresponding to amino acids 241-356 of XIAP, was mixed with 20 nM of the peptide AVPIAQKSEK-(ε-biotin)-OH 1:2 TFA, in the presence of 50 mM Tris-C1, pH 7.5, 100 mM NaCl, 1 mM dithiothreitol (DTT) and 0.1 mg/mL bovine serum albumin (BSA). Following a 45 mM incubation at 37° C., Europium-Streptavidin and Allophycocyanin conjugated anti-Histidine antibody were added to a final concentration of 1.5 nM and 15 nM, respectively. Time-resolved fluorescence resonance energy transfer (TR-FRET) signals were measured 1 hour later at room temperature. Test compound potency was assessed at 10 serially diluted concentrations. |
| Affinity data for this assay | |
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