NMR relaxation studies of receiver domain of cytokinin receptor CKI1_RD mutants from Arabidopsis thaliana

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

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

In our project, we studied the signaling pathway, called multistep phosphorelay signaling system in the plant Arabidopsis thaliana. The multistep phosphorelay signaling pathway has a great influence on many aspects of growth and development of plants. This signaling system is based on phosphate transfer between the cytoplasmatic membrane and nucleus. In the plant Arabidopsis thaliana, histidine kinase is phosphorylated upon signal recognition, and forwards the phosphate group through histidine phosphotransfer proteins to a response regulator protein located in nucleus, where the response take place. The input signal can be light,osmotic changes or hormones.

Aspartic acid 137, present in the active site of CKI1_RD, plays an important role in the signaling pathway. This Asp 137 residue binds phosphate and transfers it to next protein involved in the signaling pathway. Two CKI1_RD proteins with mutations in their active sites (CKI1_RD -D137A and CKI1_RD - D137E) were expressed in E. coli, labeled by stable isotope ¹⁵N, and studied by NMR relaxation experiments. The results were used to characterize internal motions of the mutants.

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