The NDP (nucleoside diphosphate) Sensor is a fluorescent sensor protein for the development of universal kinase assays, compound profiling, and substrate identification.

A Universal Tool for Kinase Assays

  • Universal kinase compatibility—wide range of nucleotide concentrations and protein, peptide, or lipid substrates
  • Fast and accurate—rapidly responds to ATP/ADP ratio
  • Enables endpoint or real-time kinase assays

The NDP Sensor is a coumarin-labeled form of a bacterial NDP kinase. The sensor autophosphorylates a histidine residue in the presence of NTP (nucleoside triphosphate), producing a highly fluorescent P~NDP sensor (Figure 1). The reverse reaction regenerates the unphosphorylated form. In the presence of excess nucleotides over the NDP Sensor, the ATP/ADP ratio determines the NDP Sensor phosphorylation state via fluorescence intensity.

Table 1. Z´-LYTE™-compatible monochromator-based instruments

  Tecan Safire and Safire2
Excitation filter 400/12*
Emission filter, donor 445/12*
Emission filter, acceptor 520/12*
*Wavelength in nm/bandpass
Mechanism of NDP Sensor Figure 1. Mechanism of the NDP Sensor

The NDP Sensor is an excellent universal kinase assay platform for compound profiling and screening (Figure 2), either in endpoint or kinetic mode, and can also be used to identify substrates for uncharacterized kinases (Figure 3).

Table 2. Z´-LYTE™-compatible filter-based instruments

Tecan GENios Pro™ Tecan Ultra™ series Molecular Devices Analyst® PerkinElmer EnVision™
Excitation filter 405/20* 405/20* 405/35* 400/25*
Emission filter, donor 465/35* 465/35* 460/40* 460/25*
Emission filter, acceptor 535/20* 535/20* 530/25* 535/25*
Dichroic for excitation 330/420:440/850 50% 425 General dual
Dichroic for emission 330/420:440/850 320/500:520/800 425 General dual
*Wavelength in nm/bandpass
NDP Sensor A and B
NDP Sensor C and D
Figure 2. The NDP Sensor as a universal kinase assay
The NDP Sensor enables endpoint or real-time kinase assays with peptide, protein, or lipid substrates. All fluorescence measurements were taken at 440/487 nm (Ex/Em) in 384-well plates.

A. For PKA, 20 μl reactions were monitored continuously with 10 μM ATP, 50 μM Crosstide, and 0.25 μM NDP Sensor.

B. and C
. For endpoint reads with p38α, 60 min kinase reactions were performed with 10 μM ATP and either 0.75 mg/ml myelin basic protein (MBP), 50 μM EGF-R peptide, or 500 μM EGF-R peptide, in 10 μl. For endpoint reads, 10 μl of 0.5 μM NDP Sensor was added to the reactions prior to measurements.

D. Endpoint reactions for PI3 Kinase were performed as for p38α, except that the reactions were incubated for 100 min, with 50 μM L-α-phosphatidylinositol-4,5-bisphosphate as the substrate.
Kinase Substrate Identification Figure 3. Using the NDP Sensor for kinase substrate identification