| Assay Method Information | |
| | ROCK1 and ROCK2 Kinase Inhibition Assays |
| Description: | The following assay protocol is for measuring the phosphorylation of a peptide substrate (FAM-KKLRRTLSVA-OH wherein FAM is carboxyfluorescein). The peptide is >98% purity by Capillary Electrophoresis. The peptide is phosphorylated by the protein kinase ROCK1 or ROCK2. The ROCK1 or ROCK2 enzyme, substrate, and cofactors (ATP and Mg2+) are combined in a well of a microtiter plate and incubated for 3 hours at 25° C. At the end of the incubation, the reaction is quenched by the addition of an EDTA-containing buffer. The substrate and product are separated and quantified electrophoretically using the microfluidic-based LABCHIP 3000 Drug Discovery System from Caliper Life Sciences (Hopkinton, Mass.).The components of the assay mixture are: 100 mM HEPES, pH 7.5 0.1% BSA 0.01% Triton X-100 1 mM DTT 10 mM MgCl2 10 μM Sodium Orthovanadate 10 μM Beta-Glycerophosphate 5 μM ATP (for ROCK1) or 7 μM ATP (for ROCK2) 1% DMSO (from compound) 1.25 μM FAM-KKLRRTLSVA-OH 3 nM ROCK1 or 2.5 nM ROCK2 enzymeSubstrate and product peptides present in each sample are separated electrophoretically using the LABCHIP 3000 capillary electrophoresis instrument. As substrate and product peptides are separated two peaks of fluorescence are observed. Change in the relative fluorescence intensity of the substrate and product peaks is the parameter measured reflecting enzyme activity. Capillary electrophoregramms (RDA acquisition files) are analyzed using HTS Well Analyzer software (Caliper Life Sciences, Hopkinton, Mass.). The kinase activity in each sample is determined as the product to sum ratio (PSR): P/(S+P), where P is the peak height of the product peptide and S is the peak height of the substrate peptide. For each compound, enzyme activity is measured at various concentrations (12 concentrations of compound spaced by 3× dilution intervals). Negative control samples (0%-inhibition in the absence of inhibitor) and positive control samples (100%-inhibition in the presence of 20 mM EDTA) are assembled in replicates of four and are used to calculate %-inhibition values for each compound at each concentration. Percent inhibition (Pinh) is determined using the following equation:Pinh=(PSR0%−PSRinh)/(PSR0%−PSR100%)*100where PSRinh is the product sum ratio in the presence of inhibitor, PSR/% is the average product sum ratio in the absence of inhibitor, and PSR100% is the average product sum ratio in 100%-inhibition control samples. The IC50 values of inhibitors are determined by fitting the inhibition curves (Pinh versus inhibitor concentration) by 4 parameter sigmoidal dose-response model using XLfit 4 software (IBDS). |
| Affinity data for this assay | |
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