Preparation of large volume casein kinase-2 crystals for neutron diffraction experiment

Shibazaki, Chie; Adachi, Motoyasu; Shimizu, Rumi; Kuroki, Ryota

Casein kinase 2(CK2) is one of the ubiquitous Ser/Thr kinases and is involved in the cell cycle and the survival and proliferation of cells. CK2 is a heterotetrameric structure comprising two - or -subunits. In order to understand the biological function of the alpha catalytic subunit of CK2 (CK2), we aim to analyze the structure of CK2 including information of the hydrogen and hydrating water molecule by neutron crystallography. The gene coding CK2 was inserted into pET24a and expressed in . coli strain BL21DE3, in which the mobile region (330-335) and chemically reactive thiols (Cys147 and Cys220) were removed by amino acid mutation. A total of 150 mg protein was obtained from a 6 L culture, and was used for crystallization trials. The preparation of large crystals was performed using a macro seeding method. Finally, a large crystal with a volume of approximately 2 mm was reproducibly obtained. The crystal was dialyzed in the deuterated reagent and deuterium water, and the preliminary neutron diffraction experiments were carried out at neutron beam line BioDIFF in research reactor FRM-II in Technical University of Munich. The diffraction was successfully observed greater than 1.9 resolution.