Atomic structure of a CK2alpha human kinase by microfocus diffraction of extra-small microcrystals grown with nanobiofilm template.

Extra-small microcrystals of a human kinase CK2alpha were obtained for the first time by the optimization of a recent protein crystallization method based on highly packed protein nanofilm template. Protein crystal induction and growth appear indeed optimal at high surface pressure of the film template yielding high protein orientation and packing. The resulting extra-small CK2alpha microcrystals (of about 20 microm in diameter) was subsequently used for synchrotron radiation diffraction data collection, which proves possible by means of the Microfocus Beamline at the ESRF Synchrotron in Grenoble. The quality of the resulting crystal diffraction patterns and of its resulting atomic structure at 2.4 A resolution proves the unique validity of the above two combined frontier technologies in defining a new approach to structural proteomics capable to solve the atomic structure of proteins so far never been crystallized and of pharmaceutical relevance. Physical explanation in terms of template dipole moments and possibility of generalization of this method to the wide class of proteins not yet crystallized are finally discussed. The structure of our CK2alpha mutant is in the Protein Data Bank (PDB ID Code 1NA7, deposited on 27 November 2002).