Structural and Enzymological Evidence for an Altered Substrate Specificity in Okur-Chung Neurodevelopmental Syndrome Mutant CK2αLys198Arg

Christian Werner; Alexander Gast; Dirk Lindenblatt; Anna Nickelsen; Karsten Niefind; Joachim Jose; Jennifer Hochscherf

doi:10.3389/fmolb.2022.831693

Structural and Enzymological Evidence for an Altered Substrate Specificity in Okur-Chung Neurodevelopmental Syndrome Mutant CK2α^Lys198Arg

Front Mol Biosci. 2022 Apr 4:9:831693. doi: 10.3389/fmolb.2022.831693. eCollection 2022.

Authors

Christian Werner¹, Alexander Gast², Dirk Lindenblatt¹, Anna Nickelsen², Karsten Niefind¹, Joachim Jose², Jennifer Hochscherf¹

Affiliations

¹ Department of Chemistry, Institute of Biochemistry, University of Cologne, Cologne, Germany.
² Institute of Pharmaceutical and Medicinal Chemistry, University of Münster, Münster, Germany.

Abstract

Specific de novo mutations in the CSNK2A1 gene, which encodes CK2α, the catalytic subunit of protein kinase CK2, are considered as causative for the Okur-Chung neurodevelopmental syndrome (OCNDS). OCNDS is a rare congenital disease with a high phenotypic diversity ranging from neurodevelopmental disabilities to multi-systemic problems and characteristic facial features. A frequent OCNDS mutation is the exchange of Lys198 to Arg at the center of CK2α's P+1 loop, a key element of substrate recognition. According to preliminary data recently made available, this mutation causes a significant shift of the substrate specificity of the enzyme. We expressed the CK2α^Lys198Arg recombinantly and characterized it biophysically and structurally. Using isothermal titration calorimetry (ITC), fluorescence quenching and differential scanning fluorimetry (Thermofluor), we found that the mutation does not affect the interaction with CK2β, the non-catalytic CK2 subunit, and that the thermal stability of the protein is even slightly increased. However, a CK2α^Lys198Arg crystal structure and its comparison with wild-type structures revealed a significant shift of the anion binding site harboured by the P+1 loop. This observation supports the notion that the Lys198Arg mutation causes an alteration of substrate specificity which we underpinned here with enzymological data.

Keywords: CSNK2A1 gene; P+1 loop; acidophilic substrate specificity; anion binding site; casein kinase 2; okur-chung neurodevelopmental syndrome (OCNDS); protein kinase CK2; substrate recognition.