3RPS:
reference: Enzymatic activity with an incomplete catalytic spine: insights from a comparative structural analysis of human CK2alpha and its paralogous isoform CK2alpha'., Bischoff N, Raaf J, Olsen B, Bretner M, Issinger OG, Niefind K, Mol Cell Biochem. 2011 Oct;356(1-2):57-65. Epub 2011 Jul 8. PMID: 21739153

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