TAILIEUCHUNG - Báo cáo Y học: Autophosphorylation-dependent inactivation of plant chimeric calcium/calmodulin-dependent protein kinase

Chimeric calcium/calmodulin dependent protein kinase (CCaMK) is characterized by the presence of a visinin-like Ca 2+ -binding domain unlike other known calmodulin-dependent kinases. Ca 2+ -Binding to the visinin-like domain leads to autophosphorylation and changes in the affinity for calmodulin [Sathyanarayanan ., Cremo . & Poovaiah . (2000)J. Biol. Chem. 275, 30417–30422]. Here, we report that the Ca 2+ -stimulated autophosphory-lation of CCaMK results in time-dependent loss of enzyme activity. . | Eur. J. Biochem. 269 2457-2463 2002 FEBS 2002 doi Autophosphorylation-dependent inactivation of plant chimeric calcium calmodulin-dependent protein kinase P. V. Sathyanarayanan and B. W. Poovaiah Laboratory of Plant Molecular Biology and Physiology Department of Horticulture Washington State University Pullman WA USA Chimeric calcium calmodulin dependent protein kinase CCaMK is characterized by the presence of a visinin-like Ca2 -binding domain unlike other known calmodulindependent kinases. Ca2 -Binding to the visinin-like domain leads to autophosphorylation and changes in the affinity for calmodulin Sathyanarayanan . Cremo . Poovaiah . 2000 J. Biol. Chem. 275 30417-30422 . Here we report that the Ca2 -stimulated autophosphorylation of CCaMK results in time-dependent loss of enzyme activity. This time-dependent loss of activity or self-inactivation due to autophosphorylation is also dependent on reaction pH and ATP concentration. Inactivation of the enzyme resulted in the formation of a sedimentable enzyme due to self-association. Specifically autophosphorylation in the presence of 200 M ATP at pH resulted in the formation of a sedimentable enzyme with a 33 loss in enzyme activity. Under similar conditions at pH the enzyme lost 67 of its activity and at pH 84 enzyme activity was lost. Furthermore autophosphorylation at either acidic or alkaline reaction pH lead to the formation of a sedimentable enzyme. Transmission electron microscopic studies on autophosphorylated kinase revealed particles that clustered into branched complexes. The autophosphorylation of wildtype kinase in the presence of AMP-PNP an unhydrolyz-able ATP analog or the autophosphorylation-site mutant T267A did not showformation of branched complexes under the electron microscope. Autophosphorylationdependent self-inactivation may be a mechanism of modulating the signal transduction pathway mediated by CCaMK. Keywords self-inactivation self .

• Báo cáo khoa học
• Report medicine
• traditional medicine
• scientific reports
• Crystal structure
• medical analysis
• biochemical studies
• medical knowledge
• medical research
• analysis of cytoplasmic
• oxidation
• bacteria
• hemoglobin
• medicine
• cell proliferation
• breast cancer
• chemical reaction
• gastric cancer
• hormone medicine
• tumor cells
• environmental medicine