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Updated: Jul 31, 2026

Identification of Novel CK2 Kinase Substrates Using a Versatile Biochemical Approach
Published on: February 21, 2019
Prokaryotic expression of bone sialoprotein and identification of casein kinase II phosphorylation sites
Fawzy A Saad1, Erdjan Salih, Livius Wunderlich
1Laboratory for the Study of Skeletal Disorders, Department of Orthopaedic Surgery, Harvard Medical School, Children's Hospital Boston, 300 Longwood Avenue, Boston, MA 02115, USA. fawzy.saad@tch.harvard.edu
Abstract:
Bone sialoprotein is an extracellular noncollagenous acidic protein that plays a role in bone mineralization and remodeling. Its expression is restricted to mineralized tissues and is subjected to variety of posttranslational modifications including phosphorylation and glycosylation. We have expressed the full-length and half domains of bovine bone sialoprotein in a prokaryotic system and identified the phosphorylation sites of casein kinase II. The N-terminal automated solid-phase sequencing defined four phosphorylated peptides: residues 28-38 (LEDS(P)EENGVFK), 51-86 (FYPELKRFAVQSSS(P)DS(P)S(P)EENGNGDS(P)S(P)EEEEEEEETS(P)), 151-165 (EDES(P)DEEEEEEEEEE), and 295-305 (GRGYDS(P)YDGQD). Nine phosphoserines were identified within the four peptides. Seven of them were in the N-terminus (S31, S64, S66, S67, S75, S76, and S86) and two were in the C-terminus (S154 and S300) of the protein.
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