Structure and binding specificity of the receiver domain of sensor histidine kinase CKI1 from Arabidopsis thaliana
Blanka Pekárová1,3,*, Olga Třísková2,3, Tomáš Klumpler1,3,*, Jakub Horák1,3, Radka Dopitová1,3, Séverine Jansen2,3, Lukáš Žídek2,3, Jan Hejátko1,3, Lubomír Janda1,3
Department of Functional Genomics and Proteomics, Institue of Experimental Biology1 and National Centre for Biomolecular Research2, Masaryk University, Kotlářská 2, CZ-61137 Brno, Czech Republic;
Central European Institute of Technology, Masaryk University, Žerotínovo nám. 9, CZ-60177 Brno, Czech Republic3
Multistep phosphorelay (MSP) pathway mediate sensing of wide spectrum of signals in plants, including hormonal (cytokinin, ethylene, abscisic acid) and abiotic stress regulation. In Arabidopsis MSP, the signal is transferred from sensor histidine kinase (HK) via histidine phosphotransfer proteins (AHP1-5) to nuclear response regulators. In contrast to bacteria, MSP protein interactions in plants are supposed to be rather non-specific.
A C-terminal receiver domain of histidine kinase CYTOKININ-INDEPENDENT 1 (CKI1RD) has been investigated in this study. Using both in vivo and in vitro assays we have found that CKI1RD is responsible for recognition of CKI1 downstream signaling partners and specifically interacts with AHP2, 3 and 5 with different affinities. Effects of Mg2+, the cofactor necessary for signal transduction, and phosphorylation-mimicking BeF3- on CKI1RD in solution were studied by NMR. Finally, crystal structures of free CKI1RD and CKI1RD in a complex with Mg2+ were determined. Magnesium binding induces rearrangement of some residues around the active site of CKI1RD which affects its activity and specificity.
Supported by Grants Nos. 204/08/H054, 525/07/1069, 521/09/1699, P503/10/217, P305/11/0756, MSM0021622413, MSM0021622415, LC06034, EAST-NMR, and 205872, POSTBIOMIN - FP7-REGPOT-2007-1.