Inhibitory effect and its kinetic analysis of tyrphostin AG1478 on recombinant human protein kinase CK2 holoenzyme.
OBJECTIVE
To study the direct effect of tyrphostin AG1478 [4-(3-chloroanilino)-6,7-dimethoxyquinazoline] on recombinant human protein kinase CK2 holoenzyme and its kinetics.


METHODS
Recombinant human protein kinase CK2 alpha and beta subunits were mixed at equal molar ratio and CK2 holoenzyme were reconstituted. The CK2 activity was assayed by detecting incorporation of [gamma-32P]ATP or [gamma-32P]GTP into substrates in various conditions.


RESULTS
These results demonstrated that the recombinant human CK2 was a second messengers (Ca2+, cAMP, and cGMP)-independent protein kinase, the characterization and function of the reconstituted holoenzyme were consistent with those of native CK2. AG1478 strongly inhibited the holoenzyme activity of recombinant human protein kinase CK2 with IC50 of 25.9 micromol/L, the inhibition is very close to that of N-(2-aminoethyl)-5-chloronaphthalene-1-sulfonamide (A3), but less potent than that of 5,6-dichloro-1- beta-D-ribofuranosylbenzimidazole (DRB), known as CK2 special inhibitors with IC50 of 25.5 micromol/L and 10.4 micromol/L respectively. Kinetic studies of AG1478 on recombinant human CK2 showed that inhibitions were competitive with both GTP and casein, thus AG1478 was as bisubstrate inhibitor.


CONCLUSIONS
The present study indicates that AG1478 is not only an effective inhibitor of protein tyrosine kinases of epidermal growth factor receptor (EGFR), but also a novel potent inhibitor of protein kinase CK2. The recombinant human protein kinase CK2 might be used as a molecular target for simpler screening and development of more effective inhibitors of CK2.
Liu
Xin-Guang
XG
Institute of Biochemistry and Molecular Biology, Guangdong Medical College, Zhanjiang 524023, China. xgliu@gdmc.edu.cn
Liang
Nian-Ci
NC
D047390:Casein Kinase II; D002364:Caseins / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006160:Guanosine Triphosphate / Q000378:metabolism; D020035:Holoenzymes; D006801:Humans; D007700:Kinetics; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011799:Quinazolines; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D020032:Tyrphostins / Q000494:pharmacology*
D002364:Caseins; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D020035:Holoenzymes; D011799:Quinazolines; D011994:Recombinant Proteins; D020032:Tyrphostins; C101044:RTKI cpd; D006160:Guanosine Triphosphate; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases