V. Pulgar et al., THE RECOMBINANT ALPHA-ISOFORM OF PROTEIN-KINASE CK1 FROM XENOPUS-LAEVIS CAN PHOSPHORYLATE TYROSINE IN SYNTHETIC SUBSTRATES, European journal of biochemistry, 242(3), 1996, pp. 519-528
The cDNA coding for protein kinase CK1 alpha has been cloned from a Xe
nopus laevis cDNA library. The derived amino acid sequence of the prot
ein contains 337 amino acids and has a calculated molecular mass of 38
874 Da. The sequence is identical to that of the human CK1 alpha and
to the bovine CK1 alpha, except that it is 12 amino acids longer than
the latter protein. Southern blotting with a 264-bp probe demonstrates
that four or more fragments are obtained upon digestion of genomic DN
A with EcoR1 and Hind3, suggesting that X. laevis possesses a family o
f related CK1 genes. CK1 alpha was expressed in Escherichia coli as a
glutathione transferase fusion protein (GT-CK1 alpha) and certain of i
ts characteristics were determined. The recombinant GT-CK1 alpha fusio
n protein was found to have apparent K-m values for ATP (12 mu M), cas
ein (1.5 mg/ml) and the specific peptide substrate RRKDLHDDEEDEAMSITA
(180 mu M) which are similar to those of the rat liver CK1 enzyme. The
recombinant CK1 alpha activity is weakly inhibited by heparin, but st
rongly inhibited by poly(Glu(80):Tyr(20)). This inhibition is competit
ive and shows an approximate K-i of 5 mu M. CK1 alpha can phosphorylat
e the tyrosine residues of poly(Glu(80):Tyr(20)) and the tyrosine resi
due in the synthetic peptide RRREEEYEEEE. This kinase preparation also
autophosphorylates in serine, threonine and weakly in tyrosine.