Health & Environmental Research Online (HERO)


Print Feedback Export to File
7784624 
Journal Article 
Isolation and characterization of a novel calcium/calmodulin-dependent protein kinase, AtCK, from arabidopsis 
Jeong, JC; Shin, D; Lee, J; Kang, CH; Baek, D; Cho, MJ; Kim, MC; Yun, DJ 
2007 
1 
Molecules and Cells
ISSN: 1016-8478
EISSN: 0219-1032 
24 
2 
276-282 
English 
17978582 
Protein phosphorylation is one of the major mechanisms by which eukaryotic cells transduce extracellular signals into intracellular responses. Calcium/calmodulin (Ca(2+)/CaM)-dependent protein phosphorylation has been implicated in various cellular processes, yet little is known about Ca(2+)/CaM-dependent protein kinases (CaMKs) in plants. From an Arabidopsis expression library screen using a horseradish peroxidase-conjugated soybean calmodulin isoform (SCaM-1) as a probe, we isolated a full-length cDNA clone that encodes AtCK (Arabidopsis thaliana calcium/calmodulin-dependent protein kinase). The predicted structure of AtCK contains a serine/threonine protein kinase catalytic domain followed by a putative calmodulin-binding domain and a putative Ca(2+)-binding domain. Recombinant AtCK was expressed in E. coli and bound to calmodulin in a Ca(2+)-dependent manner. The ability of CaM to bind to AtCK was confirmed by gel mobility shift and competition assays. AtCK exhibited its highest levels of autophosphorylation in the presence of 3 mM Mn(2+). The phosphorylation of myelin basic protein (MBP) by AtCK was enhanced when AtCK was under the control of calcium-bound CaM, as previously observed for other Ca(2+)/CaM-dependent protein kinases. In contrast to maize and tobacco CCaMKs (calcium and Ca(2+)/CaM-dependent protein kinase), increasing the concentration of calmodulin to more than 3 microgram suppressed the phosphorylation activity of AtCK. Taken together our results indicate that AtCK is a novel Arabidopsis Ca(2+)/CaM-dependent protein kinase which is presumably involved in CaM-mediated signaling. 
Amino Acid Sequence; Arabidopsis/drug effects/enzymology; Calcium/pharmacology; Calcium-Calmodulin-Dependent Protein Kinases/chemistry/isolation &; purification/metabolism; Calmodulin/metabolism; DNA, Complementary/isolation & purification; Manganese/pharmacology; Molecular Sequence Data; Peptides/chemistry; Phosphorylation/drug effects; Phylogeny; Protein Binding/drug effects; Protein Structure, Tertiary; Substrate Specificity/drug effects