| Assay Method Information | |
| | MPS1/PERK Biochemical Assay |
| Description: | The inhibitory activity of putative kinase inhibitors and the potency of selected compounds were determined using a trans-phosphorylation assay. Specific peptide or protein substrates are trans-phosphorylated by their specific ser-thr or tyr kinase in the presence of ATP traced with 33P-γ-ATP, and in the presence of their own optimal buffer and cofactors. The buffer for MPS1 assay was composed of HEPES 50 mM, at pH 7.5, with 2.5 mM MgCl2, 1 mM MnCl2, 1 mM DTT, 3 microM Na3VO4, 2 mM β-glycerophosphate and 0.2 mg/mL BSA. The buffer for PERK assay was composed of HEPES 50 mM, at pH 7.5 with 3 mM MgCl2, 1 mM DTT, 3 microM Na3VO4, and 0.2 mg/mL BSA. The assay was run with a final concentration MPS1 of 5 nM, in the presence of 15 microM ATP and 1.5 nM 33P-γ-ATP; the substrate was P38-βtide, used at 200 microM. The assay was run with a final concentration PERK of 8 nM, in the presence of 52 microM ATP and 2 nM 33P-γ-ATP; the substrate was eIF2alfa-tide, used at 300 microM. 384-well plates, V bottom (test plates) are prepared with 5 microL of the compound dilution (3×) and then placed onto a PlateTrak 12 robotized station (Perkin Elmer; the robot has one 384-tips pipetting head for starting the assay plus one 96-tips head for dispensing the resin) together with one reservoir for the Enzyme mix (3×) and one for the ATP mix (3×). At the start of the run, the robot aspirates 5 microL of ATP mix, makes an air gap inside the tips (2 microL) and aspirates 5 microL of MPS1 mix or 5 microL of PERK mix. The following dispensation into the plates allows the kinase reaction to start upon 3 cycles of mixing, done by the robot itself. At this point, the correct concentration is restored for all reagents. The robot incubates the plates for 60 minutes at room temperature, and then stops the reaction by pipetting 70 microL of dowex resin suspension into the reaction mix. Three cycles of mixing are done immediately after the addition of the resin. Another mixing cycle is performed after all the plates are stopped, this time using normal tips: the plates are then allowed to rest for about one hour in order to maximize ATP capture. At this point, 22 microL of the supernatant are transferred into 384-Optiplates (Perkin-Elmer), with 50 microL of Microscint 40 (Perkin-Elmer); after 5 min of orbital shaking the plates are read on a Perkin-Elmer Top Count radioactivity counter. |
| Affinity data for this assay | |
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