cPK, Cytosolic Protamine Kinase
Source: Bovine kidney
Purity: > 90% by SDS-PAGE, apparent Mr ~ 45-kDa
Supplied: 1 μg (~ 17 units) in 50 μl 50 mM Tris-HCl pH 7.0 buffer containing 14 mM β-mercaptoethanol, 1 mM benzamidine, 0.1 mM phenylmethanesulfonyl fluoride, 1 mM EDTA and 50% glycerol.
Activity: ~ 17,000 units/mg with protamine sulfate as substrate. One unit is the amount of cPK that incorporates 1 nmol of phosphate into protamine sulfate per min. Maintain preparations in aliquots at -70° C. Avoid repeated thawing.
Synonyms: Cytosolic Protamine Kinase; cPK
Figure: Sephacryl S-200 profile of a purified preparation of cPK; Activity (●—●); Protein (○—○) . The insert shows the SDS-PAGE pattern of the purified preparation. The gel was stained with Coomassie Blue. The position of marker proteins is indicated.
Background: Cytosolic Protamine Kinase (cPK) is a distinct insulin-stimulated protein kinase. This enzyme phosphorylates protein synthesis initiation factor eIF4E at serine 209 and threonine 210. It also phosphorylates hnRNP protein A1, and several other cellular proteins. cPK is itself regulated by reversible phosphorylation. It is activated by phosphorylation by MBPK-1 and MBPK-2. By contrast, PP2A1, PP2A2 and PP2AC dephosphorylate and inactivate the kinase.