Assay Report Card

ID: ALA3889252

Type: Binding

Description: Homogeneous Time Resolved-fluorescence Resonance Energy Transfer (TR-FRET) Assay: LRRK2 kinase activity is measured using a LanthaScreen kinase activity assay available from Invitrogen (Life Technologies Corporation). The assay is a homogeneous time resolved-fluorescence resonance energy transfer (TR-FRET) assay that measures phosphorylation of a fluorescein-labelled peptide substrate (fluorescein-LRRKtide, fluorescein-GAGRLGRDKYKTLRQIRQ) (SEQ ID NO 1) as a result of LRRK2 kinase activity. The phosphorylated peptide is recognized by a terbium-labelled phospho-specific anti-LRRKtide antibody and, subsequently, the phosphorylated LRRKtide can be quantified by the extent of TR-FRET between the terbium donor and fluorescein acceptor.The LRRK2 kinase is obtained from Invitrogen (Life Technologies Corporation) and comprises residues 970 to 2527 of the full length human wild-type LRRK2 kinase or a similar sequence with the G2019S mutation. As discussed above, this mutation increases the kinase activity relative to the wild-type. The kinase reactions are performed in a 20 uL volume in 384-well plates. The kinase reaction buffer consists of 50 mM Tris pH 8.5, 0.01% BRIJ-35, 10 mM MgCl2, 1 mM EGTA, and 2 mM DTT.  In the assay, 1 nM LRRK2 WT or 250 pM LRRK2 G2019S kinase is incubated with the test compound (typically at 0 to 30 uM) for 30 minutes before the kinase reaction is initiated by addition of 1.3 mM ATP and 0.4 uM fluorescein-LRRKtide. The reaction mixture (20 ul total volume) is incubated for 2 hours at 30° C. before the reaction is terminated by addition of 10 mM EDTA and 1 nM terbium-labelled anti-phospho-LRRKtide antibody (final volume 20 ul). The mixture is further incubated for 30 minutes at RT. TR-FRET is measured by excitation of the terbium-donor with 340 nm light and subsequent (delay time 100 us) measurement of terbium and fluorescein emission at 495 nm and 520 nm, respectively, over a time window of 1000 us. The measurement is repeated 10 times for fluorescein and 10 times for terbium emission with a 2000 us time window between repeats. TR-FRET measurements are performed on a Biomek Synergy plate. The TR-FRET signal is calculated as the emission-ratio at 520 nm over 495 nm.