An
in vitro protein kinase assay technology that (1) exhibits a high
assay signal to background ratio (S / B) and range (S-B); (2) is homogenous; (3) is non-radioactive; and (4) does not require a phospho-
specific antibody involves complexing a trivalent
metal ion (e.g. Ga<3+>, Fe<3+>, Al<3+>, In<3+>, Ru<3+>, Sc<3+>, Y<3+>) to the surface of amplified luminescent proximity
assay acceptor or donor beads, e.g., via a suitable
linker such as
nitrilotriacetic acid (NTA; also referred to as carboxymethyl-
lysine),
iminodiacetic acid (IDA), or an appropriately substituted N-containing heterocycle, for example a triazoheterocycle, for example a triazocyclononaneononane, such as 1-propylamino-4-acetato-1,4,7-triazacyclononane. A
protein (or constituent part) or other
kinase substrate is bound to the surface of the other of an amplified luminescent proximity assay
acceptor or donor bead and, if phosphorylated, brought into proximity with the trivalent
metal ion-complexed
acceptor bead to generate a luminescent
signal. Presence of a
kinase inhibitor inhibits
phosphorylation and therefore
signal generation and, in this way, is detectable. As the invention described herein recognizes the presence or absence of
phosphate groups on a
protein, (or constituent part), or other
biological macromolecule (e.g., mono, di, or trinucleotides, cyclic nucleotides or
phosphate substituted inositols), it is broadly applicable to any phosphorlylation or
dephosphorylation reaction enzymes and provides a highly robust and flexible assay format for protein kinases and other
enzyme classes, including
lipid kinases, phosphatases, phosphodiesterases and others.