Enzyme-linked immunosorbent assay for the measurement of JNK activity in cell extracts

Mechanism-Based Fluorescent Reporter for Protein Kinase A Detection

A novel mechanism-based fluorescent reporter was designed for the detection of protein kinase A (PKA), which is known to mediate a variety of cellular responses in most eukaryotic cells. The probe consists of a specific binding peptide sequence, LRRRRFAFC, conjugated with 2'-thioethyl-5-(or -6)-carboxyfluoresceinamide (FAMS; 2) and 5-(or 6-)carboxytetramethylrhodamine (TAMRA) at the cysteine and leucine residues, respectively. In the absence of PKA, the two fluorophores associate by hydrophobic interactions, forming an intramolecular ground-state dimer; this results in fluorescein quenching (>93 %). Upon PKA addition, the reporter reacts with the sulfhydryl functionality at Cys199 through a disulfide-exchange mechanism. FAMS is subsequently released, resulting in significant fluorescence amplification. The remaining peptide sequence, which acts as an inhibitor, is attached covalently to the enzyme. Our results suggest that this type of sensors could have far-reaching applications in the molecular sensing of enzymes.

Mass-tag technology for monitoring of protein kinase activity using mass spectrometry

Monitoring of intracellular protein kinase activity is very important for fields involving diagnosis and drug screening. However, current methods, such as radiometry using (32)P, or ELISA, are laborious and time-consuming. We have developed high-throughput assay system of protein kinase activity using mass-tagged substrate peptide probes and mass spectrometry. This assay system can easily evaluate target kinase activity and will potentially be able to simultaneously profile many protein kinase activities.