In vitro characterization of protein kinase CKII beta mutants defective in beta-beta dimerization.
Protein kinase CKII is composed of two catalytic (alpha or alpha') subunits and two regulatory (beta) subunits. The beta subunit mediates tetramer formation through beta-beta homodimerization and alpha-beta heterodimerization. In a previous study R26 and R75, point mutants of CKIIb defective in beta-beta dimerization, were isolated. In the present work we characterized these CKIIbeta mutants in vitro. Purified R26 and R75 bound to CKIIalpha but were defective in binding to CKIIbeta. R75 stimulated the catalytic activity of CKII whereas R26 gave little stimulation, and poly-L-lysine increased the stimulation of catalytic activity by R26 or R75. Circular dichroism and intrinsic fluorescence data pointed to different conformational changes in R26 and R75. Molecular modeling of these mutants provides an explanation of the difference in their ability to interact with CKIIbeta and to activate CKIIalpha.
Kim
Tae-Hyun
TH
Department of Biochemistry, College of Natural Sciences, Kyungpook National University, Daegu 702-701, Korea.
Lee
Jae-Yong
JY
Kang
Beom Sik
BS
Bae
Young-Seuk
YS
D019943:Amino Acid Substitution; D047390:Casein Kinase II / Q000737:chemistry / Q000235:genetics*; D002942:Circular Dichroism; D019281:Dimerization; D004926:Escherichia coli / Q000201:enzymology; D008958:Models, Molecular; D011189:Potassium Chloride / Q000494:pharmacology; D020836:Protein Structure, Quaternary; D013696:Temperature
D011189:Potassium Chloride; D047390:Casein Kinase II