Publication details
Effects of magnesium binding and beryllofluoridation on a component of the cytokinin signaling pathway studied by nuclear magnetic resonance
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| Year of publication | 2009 |
| Type | Conference abstract |
| MU Faculty or unit | |
| Citation | |
| Description | Cytokinins are important regulators of intrinsic developmental programs leading to de- and re-differentiation of plant cells. The cytokinin signal transduction seems to be mediated via multistep phospohorylation, similar to the action of bacterial two-component signalling systems. A soluble receiver domain of CKI1 receptor histidine kinase of Arabidopsis thaliana has been investigated by nuclear magnetic resonance (NMR) in this study. The domain was expressed in E. coli and labeled with stable isotopes (13)C, (15)N. Resonance frequencies have been assigned using standard strategy and conformational changes were monitored by running 2D (1)H-(15)N HSQC spectra. Effect of Mg(2+) has been studied in a series of titration experiments and the most significantly affected residues were identified using secondary chemical shift mapping. Activation of the protein, which cannot be studied in real time due to a short life-time of the activated form with phosphorylated aspartate, was investigated in an artificial system with phosphate replaced by beryllofluoride. In both cases, the observed chemical shift changes were mapped on a recently solved X-ray structure of the non-phosphorylated protein. In addition to the structural studies, molecular motions were investigated by N-15 NMR relaxation experiments. Series of relaxation spectra were obtained for free, Mg(2+)-bound, and beryllofluorinated protein and interpreted in terms of the Lipari-Szabo model-free approach. The observed changes are discussed in context of the X-ray structure of the free protein. |
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