3mm4

Publication Abstract from PubMed

Multistep 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^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.