Three-dimensional Structure of Mammalian Casein Kinase I: Molecular Basis for Phosphate Recognition

• Published in: Journal of molecular biology 1996-04, Vol.257 (3), p.618-631
• Main Authors: Longenecker, Kenton L., Roach, Peter J., Hurley, Thomas D.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; anion binding; casein kinase I; Casein Kinases; crystallography; Crystallography, X-Ray; Escherichia coli - genetics; Molecular Sequence Data; Mutation; Phosphorylation; Protein Conformation; protein kinase; Protein Kinases - genetics; Protein Kinases - metabolism; Sequence Analysis; Substrate Specificity
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1006/jmbi.1996.0189

The three-dimensional structure for the catalytic region of the mammalian protein kinase, casein kinase I δ (CKIδ), has been solved by X-ray crystallography to a resolution of 2.3 Å. A truncation mutant of CKIδ lacking the C-terminal autoinhibitory region was expressed in Escherichia coli, purified, and crystallized. The structure was solved by molecular replacement using the crystal structure of the catalytic domain of a CKI homolog from Schizosaccharomyces pombe, Cki1. A tungstate derivative confirmed the initial molecular replacement solution and identified an anion binding site which may contribute to the unique substrate specificity of CKI. Like other protein kinases, the catalytic domain of CKI is composed of two lobes with a cleft between them for binding ATP. Comparison of the mammalian and yeast CKI structures suggests that a rotation of the N-terminal domain occurs upon ATP binding. This domain motion is similar, but not identical, to that observed in cAMP-dependent protein kinase upon binding ATP. Although Cki1 has many similarities to CKIδ over the catalytic domain, these two forms of CKI likely perform different functions in vivo. Relating the primary sequences of other CKI enzymes to the three-dimensional architecture of CKIδ reveals a catalytic face that is especially conserved among the subset of CKI family members associated with the regulation of DNA repair.