Magnesium binding to the receiver domain of cytokinin receptor CKI1RD from Arabidopsis thaliana

Dominik Hrebík, Olga Otrusinová, Blanka Pekárová, Lubomír Janda, Jan Hejátko, and Lukáš Žídek

National Centre for Biomolecular Research, Faculty of Science and Central European Institute of Technology, Masaryk University, Kamenice 5 , CZ-62500 Brno, Czech Republic

Two component signaling system serve as stimulus system to allow an organism to respond and sense various enviromental changes and conditions. In the plant Arabidopsis thaliana, histidine protein kinase is phosphorylated upon signal recognition and forwards the phosphate group through histidine phosphotransfer proteins to a response regulator protein in nucleus, where responses take place. The input signal can be light, osmotic changes, or hormones.

We studied the receiver domain of histidine protein kinase CKI1 by nuclear magnetic resonance. The domain was expressed in E. coli and labeled with stable isotopes (¹³C, ¹⁵N). Resonance frequencies were assigned using the standart strategy. Effect of Mg²⁺, a cofactor for signal transduction, has been studied in a series of titration experiments (2D ¹H-¹⁵N HSQC spectra) and the most significantly affected residues were identified using secondary chemical shift mapping. The dissociation constant was determined.

This work was supported by grant from the Czech Science Foundation (grant No. P305/11/0756).