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Assay Method Information

Assay Name:  TR-FRET Assay
Description:  The peptide AVPIAQKSEK-(ε-biotin)-OH (SEQ ID NO: 1) 1:2 TFA (Peptide A) was identified as a substrate for the TR-FRET assay by screening the 6 Histidine-tagged (SEQ ID NO: 2) 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 (SEQ ID NO: 3) was identified as optimal for using in an assay. The peptide sequence was derivatized with biotin to provide AVPIAQKSEK-(ε-biotin)-OH (SEQ ID NO: 1) 1:2 TFA as the substrate for the TR-FRET assay.The XIAP protein sequence was obtained from the SWISS-PROT protein sequence database and the BIR2 and BIR3 domains were derived from that. The sequence of the BIR2 domain used for the TR-FRET assay is MRHHHHHHRDHFALDRPSETHADYLLRTGQVVDISDTIYPRNPAMYSEEARLKSFQNW PDYAHLTPRELASAGLYYTGIGDQVQCFACGGKLKNWEPGDRAWSEHRRHFPNCFFVL GRNLNIRSE (SEQ ID NO: 4).The sequence of the BIR3 domain used for the TR-FRET assay is MRHHHHHHRSDAVSSDRNFPNSTNLPRNPSMADYEARIFTFGTWIYSVNKEQLARAGF YALGEGDKVKCFHCGGGLTDWKPSEDPWEQHAKWYPGCKYLLEQKGQEYINNIHLTH SLEECLVRTT (SEQ ID NO: 5).Ten nanomolar of 6 Histidine-tagged (SEQ ID NO: 2) 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 (SEQ ID NO: 1) 1:2 TFA, in the presence of 50 mM Tris-Cl, pH 7.5, 100 mM NaCl, 1 mM dithiothreitol (DTT) and 0.1 mg/niL bovine serum albumin (BSA). Following a 45 min. 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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Last update November 1, 2007
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