Structure and binding specificity of the receiver domain of sensor histidine kinase CKI1 from Arabidopsis thaliana
Language English Country England, Great Britain Media print-electronic
Document type Journal Article, Research Support, Non-U.S. Gov't
- MeSH
- Arabidopsis enzymology genetics physiology MeSH
- Phosphorylation MeSH
- Phosphotransferases genetics metabolism MeSH
- Histidine metabolism MeSH
- Crystallography, X-Ray MeSH
- Protein Interaction Mapping MeSH
- Models, Molecular MeSH
- Mutation MeSH
- Protein Kinases chemistry genetics isolation & purification metabolism MeSH
- Arabidopsis Proteins chemistry genetics isolation & purification metabolism MeSH
- Recombinant Fusion Proteins MeSH
- Sensitivity and Specificity MeSH
- Signal Transduction physiology MeSH
- Protein Structure, Tertiary MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Names of Substances
- CKI1 protein, Arabidopsis MeSH Browser
- Phosphotransferases MeSH
- Histidine MeSH
- Protein Kinases MeSH
- Arabidopsis Proteins MeSH
- Recombinant Fusion Proteins MeSH
Multistep phosphorelay (MSP) signaling mediates responses to a variety of important stimuli in plants. In Arabidopsis MSP, the signal is transferred from sensor histidine kinase (HK) via histidine phosphotransfer proteins (AHP1-AHP5) to nuclear response regulators. In contrast to ancestral two-component signaling in bacteria, protein interactions in plant MSP are supposed to be rather nonspecific. Here, we show that the C-terminal receiver domain of HK CKI1 (CKI1(RD) ) is responsible for the recognition of CKI1 downstream signaling partners, and specifically interacts with AHP2, AHP3 and AHP5 with different affinities. We studied the effects of Mg²⁺, the co-factor necessary for signal transduction via MSP, and phosphorylation-mimicking BeF₃⁻ on CKI1(RD) in solution, and determined the crystal structure of free CKI1(RD) and CKI1(RD) in a complex with Mg²⁺. We found that the structure of CKI1(RD) shares similarities with the only known structure of plant HK, ETR1(RD) , with the main differences being in loop L3. Magnesium binding induces the rearrangement of some residues around the active site of CKI1(RD) , as was determined by both X-ray crystallography and NMR spectroscopy. Collectively, these results provide initial insights into the nature of molecular mechanisms determining the specificity of MSP signaling and MSP catalysis in plants.
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