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.

Department of Functional Genomics and Proteomics Masaryk University Kotlářská 2 CZ 61137 Brno Czech Republic

Citace poskytuje Crossref.org

ETR1 Integrates Response to Ethylene and Cytokinins into a Single Multistep Phosphorelay Pathway to Control Root Growth

Conformational dynamics are a key factor in signaling mediated by the receiver domain of a sensor histidine kinase from Arabidopsis thaliana

Identification of factors required for m6 A mRNA methylation in Arabidopsis reveals a role for the conserved E3 ubiquitin ligase HAKAI

Targeted in vivo inhibition of specific protein-protein interactions using recombinant antibodies

Cloning, expression, purification, crystallization and preliminary X-ray diffraction analysis of AHP2, a signal transmitter protein from Arabidopsis thaliana