Protein kinase CK2 (casein kinase 2) is a highly conserved and ubiquitously found eukaryotic serine/threonine kinase that plays a role in various cellular key processes like proliferation, apoptosis and circadian rhythm. One of its prominent biochemical properties is its ability to use GTP as well as ATP as a cosubstrate (dual-cosubstrate specificity) ...
Protein kinase CK2 (casein kinase 2) is a highly conserved and ubiquitously found eukaryotic serine/threonine kinase that plays a role in various cellular key processes like proliferation, apoptosis and circadian rhythm. One of its prominent biochemical properties is its ability to use GTP as well as ATP as a cosubstrate (dual-cosubstrate specificity). This feature is exceptional among eukaryotic protein kinases, and its biological significance is unknown. We describe here a mutant of the catalytic subunit of protein kinase CK2 (CK2alpha) from Homo sapiens (hsCK2alpha) with a clear and CK2-atypical preference for ATP compared to GTP. This mutant was designed on the basis of several structures of CK2alpha from Zea mays (zmCK2alpha) in complex with various ATP-competitive ligands. A structural overlay revealed the existence of a "purine base binding plane" harbouring the planar moiety of the respective ligand like the purine base of ATP and GTP. This purine base binding plane is sandwiched between the side-chains of Ile66 (Val66 in hsCK2alpha) and Met163, and it adopts a significantly different orientation than in prominent homologues like cAMP-dependent protein kinase (CAPK). By exchanging these two flanking amino acids (Val66Ala, Met163Leu) in hsCK2alpha(1-335), a C-terminally truncated variant of hsCK2alpha, the cosubstrate specificity shifted in the expected direction so that the mutant strongly favours ATP. A structure determination of the mutant in complex with an ATP-analogue confirmed the predicted change of the purine base binding plane orientation. An unexpected but in retrospect plausible consequence of the mutagenesis was, that the helix alpha D region, which is in the direct neighbourhood of the ATP-binding site, has adopted a conformation that is more similar to CAPK and less favourable for binding of GTP. These findings demonstrate that CK2alpha possesses sophisticated structural adaptations in favour of dual-cosubstrate specificity, suggesting that this property could be of biological significance.
Related Citations:
Crystal structure of the catalytic subunit of protein kinase CK2 from Zea mays at 2.1 A resolution Niefind, K., Guerra, B., Pinna, L.A., Issinger, O.-G., Schomburg, D. (1998) EMBO J 17: 2451
Expression, purification and crystallization of the catalytic subunit of protein kinase CK2 from Zea mays Guerra, B., Niefind, K., Pinna, L.A., Schomburg, D., Issinger, O.-G. (1998) Acta Crystallogr D Biol Crystallogr 54: 143
GTP plus water mimic ATP in the active site of protein kinase CK2 Niefind, K., Putter, M., Guerra, B., Issinger, O.-G., Schomburg, D. (1999) Nat Struct Biol 6: 1100
Crystallization and preliminary characterization of crystals of human protein kinase CK2 Niefind, K., Guerra, B., Ermakowa, I., Issinger, O.-G. (2000) Acta Crystallogr D Biol Crystallogr 56: 1680
Crystal structure of human protein kinase CK2: insights into basic properties of the CK2 holoenzyme Niefind, K., Guerra, B., Ermakowa, I., Issinger, O.-G. (2001) EMBO J 20: 5320
Expression and characterization of a recombinant maize CK-2 alpha subunit BOLDYREFF, B., MEGGIO, F., DOBROWOLSKA, G., PINNA, L.A., Issinger, O.-G. (1993) Biochim Biophys Acta 1173: 32
Cloning and sequencing of the casein kinase 2 alpha subunit from Zea mays DOBROWOLSKA, G., BOLDYREFF, B., Issinger, O.-G. (1991) Biochim Biophys Acta 1129: 139
Organizational Affiliation:
Syddansk Universitet, Institut for Biokemi og Molekylaerbiologi, Campusvej 55, DK-5230 Odense, Denmark.
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