Identification of mutations in protein kinase CKIIbeta subunit that affect its binding to ribosomal protein L41 and homodimerization.
Protein kinase CKII is composed of two catalytic (alpha or alpha') subunits and two regulatory (beta) subunits. The CKIIbeta subunit is thought to mediate the tetramer formation and interact with other target proteins. However, its physiological function remains obscure. In this study, point mutants of CKIIbeta that are defective for the L41 binding were isolated by using the reverse two-hybrid system. A sequence analysis of the point mutants revealed that Asp-26, Met-52, and Met-78 of CKIIbeta are critical for L41 binding; Asn-67 (and/or Lys-139) and Met-52 are important for CKIIbeta homodimerization. Two point mutants, R75 and R83, of CKIIbeta interacted with L5, topoisomerase IIbeta, and CKBBP1/SAG, but not with the wild-type CKIIbeta. This indicates that CKIIbeta homodimerization is not a prerequisite for its binding to target proteins. These CKIIbeta point mutants may be useful in exploring the biochemical physiological functions of CKIIbeta.
Ahn
Bong-Hyun
BH
Department of Biochemistry, College of Natural Sciences, Kyungpook National University, Daegu 702-701, Korea. ysbae@knu.ac.kr
Lee
Ji-Hoon
JH
Bae
Young-Seuk
YS
D047390:Casein Kinase II; D019281:Dimerization; D017354:Point Mutation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D012269:Ribosomal Proteins / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D020798:Two-Hybrid System Techniques
C472563:RPL41 protein, S cerevisiae; D012269:Ribosomal Proteins; D029701:Saccharomyces cerevisiae Proteins; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases