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Biochem Biophys Res Commun. 1992 Dec 15;189(2):944-9.

Recombinant rabbit muscle casein kinase I alpha is inhibited by heparin and activated by polylysine.

Author information

1
Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis 46202-5122.

Abstract

The casein kinase I (CKI) family consists of widely distributed monomeric Ser/Thr protein kinases that have a preference for acidic substrates. Four mammalian isoforms are known. A full length cDNA encoding the CKI alpha isoform was cloned from a rabbit skeletal muscle cDNA library and was utilized to construct a bacterial expression vector. Active CKI alpha was expressed in Escherichia coli as a polypeptide of Mr 36,000. The protein kinase phosphorylated casein, phosvitin and a specific peptide substrate (D4). The enzyme was inhibited by the isoquinolinesulfonamide CKI-7, half-maximally at 70 microM. Heparin inhibited phosphorylation of the D4 peptide or phosvitin by CKI alpha. Polylysine activated when the D4 peptide was the substrate but had no effect on phosvitin phosphorylation. It is becoming clear that the individual CKI isoforms have different kinetic properties and hence could have quite distinct cellular functions.

PMID:
1472067
DOI:
10.1016/0006-291x(92)92295-9
[Indexed for MEDLINE]

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