3mm4
Crystal structure of the receiver domain of the histidine kinase CKI1 from Arabidopsis thaliana
Structural highlights
FunctionCKI1_ARATH Essential protein. Functions as a histidine kinase and transmits the stress signal to a downstream MAPK cascade. This protein undergoes an ATP-dependent autophosphorylation at a conserved histidine residue in the kinase core, and a phosphoryl group is then transferred to a conserved aspartate residue in the receiver domain. Required for the development of megagametophyte in female gametophyte (embryo sac) independently of cytokinin. Contributes to vascular bundle formation and secondary growth in a cytokinin-independent manner, probably by promoting the maintenance of mitotic activity and/or identity of procambial cells. Seems to influence and promote the cytokinin signaling pathway.[1] [2] [3] [4] [5] [6] [7] Publication Abstract from PubMedMultistep phosphorelay (MSP) signaling mediates response to a variety of important stimuli in plants. In Arabidopsis MSP, the signal is transferred from sensor histidine kinase (HK) via histidine phosphotransfer proteins (AHP1-5) 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 recognition of CKI1 downstream signaling partners and specifically interacts with AHP2, AHP3, and AHP5 with different affinities. We studied the effects of Mg(2+) , the cofactor necessary for signal transduction via MSP, and phosphorylation-mimicking BeF(3) (-) on CKI1(RD) in solution and we determined the crystal structure of free CKI1(RD) and CKI1(RD) in a complex with Mg(2+) . We found that CKI1(RD) structure shares similarities with the only known structure of plant HK, ETR1(RD) , with the main differences being in loop L3. Magnesium binding induces 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 specificity of MSP signaling and MSP catalysis in plants. Structure and binding specificity of the receiver domain of sensor histidine kinase CKI1 from Arabidopsis thaliana.,Pekarova B, Klumpler T, Triskova O, Horak J, Jansen S, Dopitova R, Papouskova V, Nejedla E, Sklenar V, Marek J, Zidek L, Hejatko J, Janda L Plant J. 2011 May 13. doi: 10.1111/j.1365-313X.2011.04637.x. PMID:21569135[8] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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